Annette Walter, Michael Schuerer, Timo Eppig, Achim Langenbucher, and Holger Bruenner, "Objective approach for measuring changes in color discrimination caused by transparent colored filter media," J. Opt. Soc. Am. A 26, 2219-2225 (2009)
A novel measurement setup for determining the change in color perception due to laser protection filters is described. The developed system overcomes color space limitations common to thin-film transistor displays by using a LED illumination system, creating a large gamut covering a wide range of human color perception, and allowing adjustment of the respective spectra. An objective color matching method is used that is based on the work of
MacAdam [J. Opt. Soc. Am. A 32, 247 (1942)]
and enhanced by employing discrimination ellipses fitted on color discrimination thresholds on axes in the CIE 1976 USC chromaticity diagram. We present several measured color discrimination ellipses with and without laser protection filters.
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See text for equiment suppliers.
See text for subject and procedural information. Thirty-one people with normal color vision and two people with known congenital color deficiencies volunteered for this study. All subjects underwent testing for color deficiencies of protanomaly and deuteranomaly with the anomaloscope, with the result that all subjects with presumably normal color vision were indeed within the normal range between 34 and 46 [2]. The subjects with known color deficiencies could be identified as protanomalous (subject 1) and deuteranomalous (subject 2) [2]. The determination of the color discrimination thresholds with the described measurement system was done on two axes (b and e) around the central hue (Fig. 8). The orientations of these axes were parallel to the confusion lines of color deficient people [7].
Table 4
Comparison of Discrimination Ellipses with and without Filter T68a
Ellipse Parameter
MacAdam Data
Free Sight
T68
Center
0.185
0.249
0.174
Center
0.545
0.543
0.543
Semimajor axis
0.0013
0.003
0.005
Semiminor axis
0.0008
0.0023
0.001
ϕ (in degrees)
113.0
10.43
26.29
ϵ (eccentricity)
0.775
0.642
0.969
Accomplished by shifting the central color coordinate (not the ellipse center) to the origin of the chromaticity diagram.
Tables (4)
Table 1
Technical Data of the Seven LEDs Used for the Measurement Setupa
Color
Dominant Wavelength (nm)
CIE Color Coordinates
Max. Luminescence on Test Field
Numbers of LEDs
x
y
Blue
469
0.136
0.074
1532
6
Cyan
501
0.085
0.481
1620
5
Green
523
0.169
0.682
1735
2
Yellow
575
0.451
0.519
1515
8
Yellow
590
0.568
0.431
1595
12
Orange
603
0.649
0.349
1523
14
Red
613
0.675
0.323
1655
10
See text for instrument suppliers. Measured with a luminance and colorimetric camera and a spectrometer.
Table 2
Reliability of the Color Distancesain the (x, y) Chromaticity Diagram of 18 Subjects on Each Axis for Three Measurements
Axis
Mean Value
Std. Dev.
Mean Minimum
Mean Maximum
Cronbach’s α
1
0.0045
0.0018
0.0021
0.0093
0.701
2
0.0043
0.0018
0.0022
0.0088
0.751
3
0.0083
0.0025
0.0039
0.0130
0.731
4
0.0046
0.0021
0.0017
0.0089
0.867
5
0.0036
0.0015
0.0019
0.0086
0.880
6
0.0056
0.0023
0.0020
0.0091
0.704
Central color coordinate to the thresholds.
Table 3
Validation Measurements of Subjects with Anomaloscopea
See text for equiment suppliers.
See text for subject and procedural information. Thirty-one people with normal color vision and two people with known congenital color deficiencies volunteered for this study. All subjects underwent testing for color deficiencies of protanomaly and deuteranomaly with the anomaloscope, with the result that all subjects with presumably normal color vision were indeed within the normal range between 34 and 46 [2]. The subjects with known color deficiencies could be identified as protanomalous (subject 1) and deuteranomalous (subject 2) [2]. The determination of the color discrimination thresholds with the described measurement system was done on two axes (b and e) around the central hue (Fig. 8). The orientations of these axes were parallel to the confusion lines of color deficient people [7].
Table 4
Comparison of Discrimination Ellipses with and without Filter T68a
Ellipse Parameter
MacAdam Data
Free Sight
T68
Center
0.185
0.249
0.174
Center
0.545
0.543
0.543
Semimajor axis
0.0013
0.003
0.005
Semiminor axis
0.0008
0.0023
0.001
ϕ (in degrees)
113.0
10.43
26.29
ϵ (eccentricity)
0.775
0.642
0.969
Accomplished by shifting the central color coordinate (not the ellipse center) to the origin of the chromaticity diagram.
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