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DEVELOPMENT OF A LUMINANCE STANDARD
Antonio Corróns and Joseluis Fontecha
Instituto de Física Aplicada. (IFA-CISC)
Serrano 144, Madrid 28006, SPAIN.
Abstract
In recent decades, a major aim of the Dept. of Metrology of the IFA (CSIC) has
been the development of primary standards in optical Radiometry and Photometry. The
realizations of the Absolute Spectroradiometric Scale, the Candela and the Lumen are
all results of that work. This communication reports the development of a Luminance
Standard.
From a visual point of view, luminance is of the most important photometric
magnitude. The surfaces are visible because of their luminance.
Luminance meters need to be calibrated with respect to a reference scale, the quality of
which has a direct impact on the uncertainty of any measurements made. This work
describes the planning, construction and calibration of a Luminance Standard, basically
a luminous, circular disc with a diameter of 70 mm, backlit with diffuse light whose
spectral distribution corresponds to CIE Illuminant A.
On a smaller circle within this disc (diameter 50 mm), the uniform luminance
perpendicular to the surface
x (mm)
-40 -30 -20 -10 0 10 20 30 40
achieved was better than 1%
40
(measured using a fibre optic
L v
(%)
30
system with Cartesian
20
100.25 - 100.30
movement) (Fig. 1). The
100.20 - 100.25
100.15 - 100.20
10
100.10 - 100.15
luminance at each point
100.05 - 100.10
100.00 - 100.05 100,3 100,2 100,1 99,9 99,8 100,0 99,7
0
99.95 - 100.00
complied with Lambert’s Law
99.90 - 99.95
99.85 - 99.90
-10
99.80 - 99.85
into an angular interval of ± 15º
99.75 - 99.80
-20
99.70 - 99.75
with respect to the normal to
-30
the surface.
-40
y (mm)
Figure 2 shows the
temporal stability of the
emitting surface.
Fig. 1.- Relative luminance on the surface of
Luminance Standard.
Proceedings NEWRAD, 17-19 October 2005, Davos, Switzerland 203