Fundamentals of spectroradiometry and colorimetry
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Transcript Fundamentals of spectroradiometry and colorimetry
Fundamentals of
spectroradiometry and
colorimetry
János Schanda
Spectroradiometry
Publication
CIE 63-1984:
The spectroradiometric measurement of
light sources
– The spectroradiometer
– Basic principles of measurement
– Bandwidth considerations
Colorimetry - Division 1
Publication
–
–
–
–
CIE 15.2-1986: Colorimetry
Standard illuminants
Standard observers
Calculation of tristimulus values
Uniform colour spacing
TC
1-36: New chromaticity diagram
TC 1-38: Tabulation of spectral data
Report on Improved Colorimetry
Colorimetry - Division 2
TC
2-04: Secondary standard sources
TC 2-16: Characterization of the
performance of tristimulus colorimeters
TC 2-33, -35: Standard illuminants and
V(l) & V’(l)
TC 2-39: Geometric tolerances for
colorimetry
Spectroradiometry of LEDs
Spectral
irradiance measurement
Spectral radiance and flux measurement
The spectroradiometer
Measurement principles
Practical measurements
Colorimetry of LEDs
Fundamentals
of CIE colorimetry
Light source colorimetry
A new system of colorimetry?
Reportership: Improved colorimetry
Work in CIE TC 1-36: Fundamental
chromaticity diagram with
physiologically significant axes
The spectroradiometer system
Input optical arrangement-1
Input optical arrangement-2
Monochromators - 1
Light
grasp or etendu, throughput,
efficiency:
(l ) h A d
Z (l )
.
f
dl
Double
monochromator:
– Two gratings (additive, subtractive
dispersion)
– grating + prism
Monochromators - 2
Stray
radiation
Determination with
– Interference filter:
– Sharp cut-off filters
– Lasers
Wavelength
s
R2 T (l )
1
(l )
R1
accuracy: +/- 0,1 nm
– stability
– temperature dependence: 0,1 - 0,5 nm/C°
Detector and measuring system
Irradiation
of detector - homogeneity
Type of detector: photomultiplier, Si-cell
– linearity (superposition)
– temperature dependence
– high voltage stability
Standard
sources
Method of measurement
Method of measurement
Sequence:
test - standard
Transmittance function - Bandwidth
Bandwidth & sampling
Continuous scan method
Practical measurements - Errors
Stray
light
Wavelength error
Bandwidth - interpolation, extrapolation
Polarization
Detector system
Reference standard
Colorimetry
Additive
colour mixture
Laws of additive colour
matching
Symmetry
law:
If A B then B A
Transitivity law:
If A B and B C then A C
Proportionality law:
If A B then A B
Additivity
law:
If A B, C D, or A C B D
then A D B C
Grassmann’s laws
To
specify a colour match three independent
variables are necessary and sufficient
For additive mixture of colour stimuli, only
their tristimulus values are relevant, not
their spectral composition
In additive mixtures of colour stimuli, if one
or more components are gradually changed,
the resulting tristimulus values also change
gradually
Colour equation - 1
Positive
additivity
C R R G G B B
Colour equation - 2
External
colour mix - negative additivity
C R R G G B B
Colour equation - 3
Two
spectral lights:
C(l 1) C(l 2) R1 R2 R G1 G2 G B1 B2 B
Many
spectral lights:
Rk
Gk
Bk
780 nm
P(l )
380 nm
780 nm
P(l )
380 nm
780 nm
P(l )
380 nm
r ( l ) l
g ( l ) l
b ( l ) l
Colour equation - 4
Integral
form:
780nm
Ti k
el ti (l ) dl ,
380nm
with three t values
Three real primaries with
L = 1,000R + 4,5907G + 0,601B
R, G, B colour space
RGB - XYZ transformation
X
Y
Z
2 ,76888 1,75175
1,00000
113016
,
R
4 ,59070 0,06010 G
0,00000 0,05651 5,59427
...
B
1,80
1,60
1,40
x2(lambda)
rel. sens.
1,20
1,00
y2(lambda)
0,80
z2(lambda)
0,60
0,40
0,20
0,00
350
400
450
500
550
600
650
wavelength, nm
700
750
800
850
A new system of colorimetry?
TC
1-36: Physiologically significant ...
1
log cone action sensitivity
0
-1
-2
L-cone
-3
M-cone
-4
S-cone
-5
-6
-7
-8
350
450
550
wavelength, nm
650
750
Improved colorimetry?
Luminance-brightness
Additivity
discrepancy
problems
New colour matching functions?
Individual variations
Highly metameric matches
Colour appearance models
TC 1-36: Physiologically significant
...
L, M, S primaries based on
psychophysical measurements:
König hypothesis - congenital dichromats
Photopigment spectral absorbance
Selective absorption by the lens
Selective absorption by the macular
pigment
Thanks for your attention