Fundamentals of spectroradiometry and colorimetry János Schanda.
Transcript of Fundamentals of spectroradiometry and colorimetry János Schanda.
Fundamentals of spectroradiometry and colorimetry
János Schanda
SpectroradiometrySpectroradiometry
Publication CIE 63-1984:The spectroradiometric measurement of light sources– The spectroradiometer– Basic principles of measurement– Bandwidth considerations
Colorimetry - Division 1Colorimetry - 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 2Colorimetry - 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() & V’() TC 2-39: Geometric tolerances for
colorimetry
Spectroradiometry of LEDsSpectroradiometry of LEDs
Spectral irradiance measurement Spectral radiance and flux measurement The spectroradiometer Measurement principles Practical measurements
Colorimetry of LEDsColorimetry 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 systemThe spectroradiometer system
Input optical arrangement-1Input optical arrangement-1
Input optical arrangement-2Input optical arrangement-2
Monochromators - 1
Light grasp or etendu, throughput, efficiency:
Double monochromator: – Two gratings (additive, subtractive dispersion)– grating + prism
Zh A
f( )
( ).
d
d
Monochromators - 2
Stray radiationDetermination with– Interference filter:– Sharp cut-off filters– Lasers
Wavelength accuracy: +/- 0,1 nm– stability– temperature dependence: 0,1 - 0,5 nm/C°
s
( )
( )
R T
R2
11
Detector and measuring systemDetector 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 measurementMethod of measurement
Sequence: test - standard Transmittance function - Bandwidth
Bandwidth & samplingBandwidth & sampling
Continuous scan methodContinuous scan method
Practical measurements - ErrorsPractical 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:
Transitivity law:
Proportionality law:
Additivity law:
If thenA B B A
If and thenA B B C A C
If thenA B A B
If or
then
A B C D A C B D
A D B C
, ,
Grassmann’s lawsGrassmann’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 G B B R G
Colour equation - 2
External colour mix - negative additivity C R G B R G B
Colour equation - 3
Two spectral lights:
Many spectral lights:
C C R R G G B B( ) ( ) 1 2 1 2 1 2 1 2 R G B
R k P r
G k P g
B k P b
( ) ( )
( ) ( )
( ) ( )
380 nm
780 nm
380 nm
780 nm
380 nm
780 nm
Colour equation - 4
Integral form:
with three t values Three real primaries with
L = 1,000R + 4,5907G + 0,601B
T k ti i e
nm
780nm
d 380
( ) ,
R, G, B colour space
RGB - XYZ transformation
wavelength, nm
rel.
sen
s.
0,00
0,20
0,40
0,60
0,80
1,00
1,20
1,40
1,60
1,80
350 400 450 500 550 600 650 700 750 800 850
x2(lambda)
y2(lambda)
z2(lambda)
A new system of colorimetry?
TC 1-36: Physiologically significant ...
-8
-7
-6
-5
-4
-3
-2
-1
0
1
350 450 550 650 750
wavelength, nm
log
co
ne
ac
tio
n s
en
sit
ivit
y
L-cone
M-cone
S-cone
Improved colorimetry?Improved colorimetry?
Luminance-brightness discrepancy Additivity 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