Measurement of the photometric characteristics of LEDs
Proposed and implemented a method for measuring LEDs, which is based on self-calibration of the LED goniophotometer facility by using a trap-detector. Designed and manufactured automated goniophotometer, which provides a measurement of high power LEDs at a specified junction temperature. Designed an...
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Nazarenko, L.A. Zubkov, D.P. 2017-01-20T18:15:02Z 2017-01-20T18:15:02Z 2015 Measurement of the photometric characteristics of LEDs / L.A. Nazarenko, D.P. Zubkov // Вопросы атомной науки и техники. — 2015. — № 6. — С. 141-145. — Бібліогр.: 7 назв. — англ. 1562-6016 PACS: 07.60.-j, 07.60.Dq https://nasplib.isofts.kiev.ua/handle/123456789/112377 Proposed and implemented a method for measuring LEDs, which is based on self-calibration of the LED goniophotometer facility by using a trap-detector. Designed and manufactured automated goniophotometer, which provides a measurement of high power LEDs at a specified junction temperature. Designed and experimentally researched the photometer with a photometric sphere based diffuser, which meets all requirements of CIE for photometric measurements of LEDs. Запропоновано та реалізовано метод вимірювання світлодіодів, який полягає в самокалібруванні гоніофотометричної установки для вимірювання світлодіодів за допомогою трап-детектора. Розроблено та виготовлено автоматизований гоніофотометр, який забезпечує вимірювання потужних світлодіодів при заданій температурі p-n-переходу. Розроблено та експериментально досліджено фотометр з фотометричною кулею в якості дифузора, який відповідає всім вимогам МКО для фотометричних вимірювань світлодіодів. Предложен и реализован метод измерения светодиодов, который заключается в самокалибровке гониофотометрической установки для измерения светодиодов с помощью трап-детектора. Разработан и изготовлен автоматизированный гониофотометр, который обеспечивает измерение мощных светодиодов при заданной температуре p-n-перехода. Разработан и экспериментально исследован фотометр с фотометрической сферой в качестве диффузора, который отвечает всем требованиям МКО для фотометрических измерений светодиодов. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Экспериментальные методы и обработка данных Measurement of the photometric characteristics of LEDs Вимірювання фотометричних характеристик світлодіодів Измерение фотометрических характеристик светодиодов Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| title |
Measurement of the photometric characteristics of LEDs |
| spellingShingle |
Measurement of the photometric characteristics of LEDs Nazarenko, L.A. Zubkov, D.P. Экспериментальные методы и обработка данных |
| title_short |
Measurement of the photometric characteristics of LEDs |
| title_full |
Measurement of the photometric characteristics of LEDs |
| title_fullStr |
Measurement of the photometric characteristics of LEDs |
| title_full_unstemmed |
Measurement of the photometric characteristics of LEDs |
| title_sort |
measurement of the photometric characteristics of leds |
| author |
Nazarenko, L.A. Zubkov, D.P. |
| author_facet |
Nazarenko, L.A. Zubkov, D.P. |
| topic |
Экспериментальные методы и обработка данных |
| topic_facet |
Экспериментальные методы и обработка данных |
| publishDate |
2015 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Вимірювання фотометричних характеристик світлодіодів Измерение фотометрических характеристик светодиодов |
| description |
Proposed and implemented a method for measuring LEDs, which is based on self-calibration of the LED goniophotometer facility by using a trap-detector. Designed and manufactured automated goniophotometer, which provides a measurement of high power LEDs at a specified junction temperature. Designed and experimentally researched the photometer with a photometric sphere based diffuser, which meets all requirements of CIE for photometric measurements of LEDs.
Запропоновано та реалізовано метод вимірювання світлодіодів, який полягає в самокалібруванні гоніофотометричної установки для вимірювання світлодіодів за допомогою трап-детектора. Розроблено та виготовлено автоматизований гоніофотометр, який забезпечує вимірювання потужних світлодіодів при заданій температурі p-n-переходу. Розроблено та експериментально досліджено фотометр з фотометричною кулею в якості дифузора, який відповідає всім вимогам МКО для фотометричних вимірювань світлодіодів.
Предложен и реализован метод измерения светодиодов, который заключается в самокалибровке гониофотометрической установки для измерения светодиодов с помощью трап-детектора. Разработан и изготовлен автоматизированный гониофотометр, который обеспечивает измерение мощных светодиодов при заданной температуре p-n-перехода. Разработан и экспериментально исследован фотометр с фотометрической сферой в качестве диффузора, который отвечает всем требованиям МКО для фотометрических измерений светодиодов.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/112377 |
| citation_txt |
Measurement of the photometric characteristics of LEDs / L.A. Nazarenko, D.P. Zubkov // Вопросы атомной науки и техники. — 2015. — № 6. — С. 141-145. — Бібліогр.: 7 назв. — англ. |
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| fulltext |
ISSN 1562-6016. ВАНТ. 2015. №6(100) 141
MEASUREMENT OF THE PHOTOMETRIC CHARACTERISTICS
OF LEDs
L.A. Nazarenko, D.P. Zubkov
O.M. Beketov National University of Urban Economy in Kharkov, Kharkov, Ukraine
E-mail: lnazarenko@ksame.kharkov.ua; dmytro@z-ldc.com.ua
Proposed and implemented a method for measuring LEDs, which is based on self-calibration of the LED gonio-
photometer facility by using a trap-detector. Designed and manufactured automated goniophotometer, which pro-
vides a measurement of high power LEDs at a specified junction temperature. Designed and experimentally re-
searched the photometer with a photometric sphere based diffuser, which meets all requirements of CIE for photo-
metric measurements of LEDs.
PACS: 07.60.-j, 07.60.Dq
FOREWORD
The rapid development of light-emitting diodes
(LEDs) revealed the problem of the lack of accurate and
reliable methods for measuring the photometric charac-
teristics of LEDs. Their unusual photometric parame-
ters, such as spectrum radiation, spatial luminous inten-
sity distribution, and others, have led to the fact that
existing methods and measurement means that were
developed for incandescent lamps have become unusa-
ble for LEDs. Trying to compare the results of photo-
metric measurements in various National Metrology
Institutes revealed a difference in measurement results
up to several tens of percent. In the framework of inter-
national cooperation by the International Commission
on Illumination (CIE), general guidelines were devel-
oped for measuring LEDs – CIE 127-2007 "Photometry
LEDs" [1]. These recommendations contain only a gen-
eral concept which results in each country solving the
problem of measuring photometric characteristics of
LEDs by developing their own techniques.
It is also important to have appropriate measurement
means that are traceable to the national standards, the
comparisons of which on an international scale, pro-
vides the required accuracy of measurements and unity
of the measured results throughout the world. Therefore,
an important and urgent task is to create methods and
means for measurement of LEDs that would on the one
hand meet the requirements of the CIE, and on the oth-
er, are traceable to the national standards, providing the
required accuracy and traceability of measurement re-
sults.
1. GONIOPHOTOMETER LGF-C-42
It is still the unanswered question – which character-
istics should have a reference means for measurement of
LEDs? In the world measurement practice, the greatest
success on this issue was reached by the National Insti-
tute of Standards and Technology (NIST) (US) and
Physical-Technical Institute (PTB) (Germany). In the
NIST, as a standard means for measuring the average
LED intensity, reference photometers were used with
aperture area of 100 mm2. Measurement of luminous
flux of LEDs is performed using NIST 2.5 m absolute
integrating sphere, based on the absolute measurement
method [2].
In PTB the measurements of LEDs are made on spe-
cially designed goniophotometer which are also used to
measure luminous flux of LEDs [3].
To measure the luminous flux of LEDs, (the most
important parameter for light sources) the integrating
sphere method is attractive enough because of the
speed, however, to perform precision measurements it is
necessary to use the luminous flux standard. Goniopho-
tometry is an absolute method for measurement of total
luminous flux and does not require luminous flux stand-
ards. A photometer scans over an imaginary spherical
surface around the test LED and measures the illumi-
nance distribution. The measured illuminance is then
integrated over the entire spherical surface to calculate
the total luminous flux. Goniophotometry tends to be
more accurate at measuring varieties of light sources but
is more time-consuming than sphere photometry. The
creation of a measuring device based on goniophoto-
metric method for measuring luminous flux of LED is
most appropriate.
For these purposes, LED Goniophotometer Facility
LGF-C-42 was designed and created, to measure the
photometric characteristics of LEDs (Fig. 1). The re-
quired software was also developed.
Fig. 1. LED Goniophotometer Facility LGF-C-42
The rotating mechanism was created using two step-
per motors and reducers. The Goniophotometer resolu-
tion to change planes C-equal 0.00014º, the resolution
to change γ-angles equal 0.08º, which is sufficient for
most measurements.
The test LED was mounted on the mounting plate of
the thermostat via printed circuit boards "Star" or the
like. The required temperature level can be set and
maintained using a Peltier element. In the lateral plane
of the mounting plate, temperature sensor DS18B20 was
installed, to provide feedback between the thermostat
mailto:lnazarenko@ksame.kharkov.ua
ISSN 1562-6016. ВАНТ. 2015. №6(100) 142
control unit and the computer on which the program for
management and monitoring temperature was run. Us-
ing the thermostat, measurement of photometric charac-
teristics of high-power LEDs at specified constant junc-
tion temperature was performed in accordance to a
method developed by NIST [4].
2. SPHERE-PHOTOMETER
For photometers that are used to measure average
LED intensity, there is a requirement of sensitivity uni-
formity within the aperture [1]. This requirement is
caused by the presence of certain types of LED narrow
beam distribution or non-uniform spatial distribution of
intensity, that create non-uniform distribution of light
within the surface of aperture opening.
Usually non-uniformity of the sensitivity within the
photometer sensitive area is 0.1% or less when using
photometric sphere as the diffuser. This gives 3-5 times
better uniformity of the sensitivity than silicon photodi-
odes highest quality [5].
In view of the above, the advantages of the photo-
metric sphere as diffuser becomes apparent, therefore
the photometer was designed and manufactured to use
such a photometric sphere (Fig. 2, Table 1).
Filter
Photodiode
Sphere unit
Ç85mm
Input baffle tube
Precision
aperture
Port for
spectrometer
Filter
Photodiode
Sphere unit
Ç85mm
Input baffle tube
Precision
aperture
Port for
spectrometer
Fig. 2. Sphere-photometer
The detector used in the photometer was the photo-
diode Hamamatsu S1337-1010BQ. Since the S1337
series photodiodes are not corrected to the CIE V(λ)
function, a filter based on a set of colored optical glass-
es was calculated and manufactured. Given the influ-
ence of the sphere coating (paint OPRC from OptoPol-
ymer), f1' was calculated equal to 5.86%, and measured
– 5.83%. This result is more dependent on the quality of
colored glasses, so in future it can be improved.
For amplification of the output signal from the pho-
tometer a transimpedance amplifier was designed based
on the operational amplifier AD549JHZ. As the feed-
back resistance, precision 100 MOhm resistor was used.
To automate the measurement process on the gonio-
photometer facility LGF-C-42, appropriate software was
created (Fig. 3) that allows automatic (according to the
preset settings) measurement of the spatial light intensi-
ty distribution of the test LED. During measurement, the
operator can monitor the process and measurement re-
sults in the software’s main window.
Table 1
Characteristics of the created sphere-photometer
Characteristics Designation Value
V(λ) match f1’ 5.825%
Cosine response f2 0.0089%
Linearity error f3 0.07%
Temperature coeffi-
cient Α 0.012%/°С
Fatigue f5 0.146%
Modulated radiation f7 0.1%
Effect of nonuniform
illumination of the ac-
ceptance area of a pho-
tometer head
f9 0.41%
Fig. 3. Goniophotometer LGF-C-42 software
After measurement ends, the results can be saved in
*.xml spreadsheet format or as IES-file. The latter al-
lows use of measuring results in programs for lighting
simulation, such as Photopia, Zemax or TracePro.
3. SPHERE-PHOTOMETER CALIBRATION
For the traceability of the results to the state primary
standards it was decided to use the standard detector
method, which is more versatile than the method of
standard light source. This method has the following
advantages: the unit of the measured value remains on
the photometer, which is more stable over time and it
has a long service life and requires smaller service costs.
The issue of transmission scale from the standard
detector to the test detector, down to comparing the re-
action of the test detector and the standard detector
measured at each wavelength of the desired spectral
range and spectral characteristics determine the ratio of
photocurrent / power of radiation incident on the test
detector, i.e. its spectral characteristics A/W sensitivi-
ty [6].
To transfer the scale from the standard detector to
the test detector a spectral comparator facility was de-
signed (Fig. 4), which uses the substitution method with
monitor-detector.
As a reference detector the designed trap-detector
[7] was used, which consists of three silicon photodi-
odes Hamamatsu S1337-1010BQ. The trap-detector
allows reproduction of the scale of radiation power in
range from 10-9 to 10-2 W in the visible range. Margin of
main relative measurement error is ± 0.2%.
ISSN 1562-6016. ВАНТ. 2015. №6(100) 143
Fig. 4. Spectral comparator facility
As a test detector, photometric head with silicon
photodiode Hamamatsu S1337-1010BR and precision
aperture were used. After calibration, this photometer is
used as a working standard for calibration of photome-
ters in other measurement devices.
With spectral power responsivity of the working
standard, it’s easy to find the integral value of the lumi-
nous flux that was measured during calibration. Thus,
knowing the exact value of the aperture acceptance area,
it is possible to calculate the integral value of illumi-
nance on the aperture acceptance area of the working
standard.
Calibration of the photometer of LGF-C-42 is made
by the working standard detector using the method of
substitution. For calibration of the test detector, it is set
alternately with the working standard detector at equal
distance from the standard illuminant type A.
Equation of the illuminance responsivity of the
sphere-photometer LGF-C-42 is shown below:
( )
( )LGFs
s
s
ssLGF
LGF
LGF
LGF
l
R
U
Sl
R
U
S
α
α
cos
cos
2
2
⋅⋅
⋅⋅⋅
= , (1)
where ULGF – voltage on exit of LGF-C-42 transim-
pendance amplifier; RLGF – feedback resistance of LGF-
C-42 transimpendance amplifier; lLGF – distance be-
tween standard illuminant type A and the aperture ac-
ceptance area of LGF-C-42 photometer; αLGF – angle of
deviation from the optical axis of LGF-C-42; Us – volt-
age on exit of working standard detector transimpend-
ance amplifier; Rs – feedback resistance of working
standard detector transimpendance amplifier; ls – dis-
tance between standard illuminant type A and the aper-
ture acceptance area of working standard detector; αs –
angle of deviation from the optical axis of working
standard detector; Ss – illuminance responsivity of the
working standard detector.
The illuminance responsivity of the sphere-
photometer LGF-C-42 equals 1.804451·10-10 [A/lx].
The uncertainty budget for calibration is presented in
Table 2.
Table 2
Uncertainty budget for sphere-photometer calibration
Uncertainty component Relative standard uncertainty
(type B), %
Voltage on exit of LGF-C-42 transimpendance amplifier 0.005
Feedback resistance of LGF-C-42 transimpendance amplifier 0.085
Distance between light source and the aperture of LGF-C-42 photometer 0.191
Angle of deviation from the optical axis of LGF-C-42 0.001
Voltage on exit of working standard detector transimpendance amplifier 0.005
Feedback resistance of working standard detector transimpendance amplifier 0.042
Distance between light source and the aperture acceptance area of working stand-
ard detector 0.191
Angle of deviation from the optical axis of working standard detector 0.001
Illuminance responsivity of the working standard detector 0.203
Cosine response 0.005
Linearity error 0.040
Temperature coefficient (for Tamb =18°С) 0.048
Fatigue 0.084
Modulated radiation 0.058
Effect of nonuniform illumination of the acceptance area of a photometer head 0.237
Relative expanded uncertainty of calibration U (k=2) 0.88
4. LEDs MEASUREMENTS
Measurement of high-power LEDs, including (if
necessary) averaged luminous intensity performed at a
goniometer zero position in which the mechanical axis
of the test LED is aligned to the photometric axis of
sphere-photometer. The equation used for measurement
of luminous intensity on goniophotometer LGF-C-42 is
obtained by:
( )αcos
* 2
0 rF
SR
UUI
LGFLGF
LED
⋅
⋅
⋅
−
= , (2)
where U and U0 – measured and dark signal respective-
ly; RLGF – feedback resistance of LGF-C-42 transim-
pendance amplifier; SLGF – illuminance responsivity of
the sphere-photometer LGF-C-42; F* – spectral mis-
match correction factor; r – distance between LED and
the aperture acceptance area of LGF-C-42 photometer;
α – deviation angle from the optical axis of LGF-C-42.
Spectral mismatch correction factor F* calculated
for each test LED as given by
( ) ( )
( ) ( )
( ) ( )
( ) ( )∫
∫
∫
∫
⋅
⋅
⋅
⋅
⋅
=
λλλ
λλλ
λλλ
λλλ
dVS
dsS
dsS
dVS
F
A
relA
rel
* , (3)
ISSN 1562-6016. ВАНТ. 2015. №6(100) 144
where S(λ) – the relative spectral distribution of the test
LED; SA(λ) – the relative spectral distribution of the
CIE standard illuminant type A; V(λ) – the CIE spectral
luminous efficiency function of the photopic vision;
srel(λ) – the relative spectral responsivity of the photom-
eter head.
Table 3
Uncertainty budget for luminous intensity measurements of high-power LED
Uncertainty
component Type Probability
distribution
Standard uncertainty
of an input quantity
Relative sensitivi-
ty coefficient
Relative standard
uncertainty, %
Measured signal B Rectangular 0.00015 -0.36229 0.005
Dark signal B Rectangular 3.5·10-6 -0.36229 0.0001
Feedback resistance
of amplifier
B Normal 84394.26 -1 · 10-8 0.0845
Calibration of sphere-
photometer
B Normal 7.9·10-13 -5.5·10-9 0.44
Spectral mismatch
correction factor
B Normal 0.007 0.98814 0.6928
Distance measure-
ment
B Rectangular 0.00087 3.04535 0.2641
Combined relative standard uncertainty, % 0.87
Expanded uncertainty U (k = 2), % 1.73
For the measurement of luminous flux on gonio-
photometer LGF-C-42 the same steps of preparatory
work must be performed as for luminous intensity
measurements. The only difference is that LED in-
tensity is measured in all directions. To calculate the
luminous flux the measurement equation used is:
( ) )cos(cos,2 21
0
2 θθϕθπ
π
θ
−= ∑
=
ErФv
, (4)
where r – distance between LED and photome-
ter [m]; E – illuminance on sphere-photometer aper-
ture [lx]; θ, φ – coordinates of luminous intensity
direction in spherical coordinates system.
Since most of the factors that affect the measure-
ment of luminous flux of LEDs are identical with the
corresponding effects in measuring the luminous in-
tensity, the latter is used without changes. Additional-
ly consideration is only needed for the scanning step
and influence of changing the ambient light that de-
pend on the position of the LED (see Tables 3, 4).
Table 4
Uncertainty budget for luminous flux measurements of high-power LED
Uncertainty component Type Probability distribution Relative standard uncer-
tainty, %
Uncertainty of luminous
intensity measurements
B Normal 0.87
Scanning step and lumi-
nous flux calculation
B Rectangular 0.06
Stray light influence B Rectangular 0.12
Combined relative standard uncertainty, % 0.88
Expanded uncertainty U (k = 2), % 1.78
CONCLUSIONS
As a result of this work a goniophotometer facility
for measuring photometric characteristics of high-power
LEDs was designed created and experimentally re-
searched. This facility meets all requirements described
in CIE 127-2007 and also meets global trends of these
type of measurements. The goniophotometer facility
allows measuring high-power LEDs at desired junction
temperature using the method developed by NIST. All
measuring processes are controlled from a PC by using
specially developed software.
The proposed, created and experimentally re-
searched unique sphere-photometer also satisfies the
requirements of CIE with regards to measurement pho-
tometry of LEDs, and combines the functions of the
input optics for photometer and for the spectrometer.
The Sphere-photometer calibration was achieved by
using developed self-calibrated trap-detector, that pro-
vides traceability of measurement results to the primary
standards of Ukraine.
REFERENCES
1. Measurement of LEDs: CIE 127-2007. 2007, 38 p.
2. C. Cameron Miller, Yuqin Zong, Yoshihiro Ohno.
LED photometric calibrations at the National Insti-
tute of Standards and Technology and future meas-
urement needs of LEDs // Fourth Intern. Conf. on
Solid State Lighting: Proc. of SPIE. Bellingham,
WA. 2004, v. 5530, p. 69-79.
3. G. Zauter, M. Lindemann, Y. Ohno, A. Sperling.
Photometry of LEDs // Svetotekhnyka. 2004, № 3,
p. 5-11 (in Russian).
4. Y. Zong, Y. Ohno. New practical method for meas-
urement of high-power LEDs // CIE Expert Symp.
2008 on Advances in Photometry and Colorimetry /
CIE x033:2008. Turin, 2008.
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5. Optical Radiometry. Experimental Methods in the
Physical Sciences / Ed. by A.C. Parr, R.U. Datla,
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cation 250-41. Gaithersburg: NIST, 2008, 120 p.
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ing and power engineering. 2011, № 2, p. 34-38.
Article received 05.06.2015
ИЗМЕРЕНИЕ ФОТОМЕТРИЧЕСКИХ ХАРАКТЕРИСТИК СВЕТОДИОДОВ
Л.А. Назаренко, Д.П. Зубков
Предложен и реализован метод измерения светодиодов, который заключается в самокалибровке гонио-
фотометрической установки для измерения светодиодов с помощью трап-детектора. Разработан и изготов-
лен автоматизированный гониофотометр, который обеспечивает измерение мощных светодиодов при задан-
ной температуре p-n-перехода. Разработан и экспериментально исследован фотометр с фотометрической
сферой в качестве диффузора, который отвечает всем требованиям МКО для фотометрических измерений
светодиодов.
ВИМІРЮВАННЯ ФОТОМЕТРИЧНИХ ХАРАКТЕРИСТИК СВІТЛОДІОДІВ
Л.А. Назаренко, Д.П. Зубков
Запропоновано та реалізовано метод вимірювання світлодіодів, який полягає в самокалібруванні гоніо-
фотометричної установки для вимірювання світлодіодів за допомогою трап-детектора. Розроблено та виго-
товлено автоматизований гоніофотометр, який забезпечує вимірювання потужних світлодіодів при заданій
температурі p-n-переходу. Розроблено та експериментально досліджено фотометр з фотометричною кулею в
якості дифузора, який відповідає всім вимогам МКО для фотометричних вимірювань світлодіодів.
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