Personnel
Professor David Atchison
Professor Joanne Wood
Dr Andrew Zele
Dr Huanqing Guo
Ms Preeti Gupta (graduate student)
Collaborator
Professor Stephen Dain (UNSW)
Scope
The Colour Vision research group is located within the Institute of Health and Biomedical Innovation at QUT and is part of the Institute’s Vision Improvement Domain. Its objective is the investigation of interesting colour vision phenomena.
Current Projects
Sunglass Tints and Driving Performance
Professors Atchison, Wood and Dain are investigating the influence of sunglass coloration on the driving ability of people with normal and deficient colour vision. A laboratory experiment compared traffic signal recognition of colour normals and people with colour vision deficiencies for different sunglass tints. Figure 1 shows response times (top) and error rates (bottom) for colour normals and deuteranopes. For clear lenses and neutral grey lenses, the deuteranopes perform much more poorly than do the normals. This is exacerbated with the green, yellow-green, yellow-brown and red-brown sunglass tints [1,2].
This study has implications for Australian and international sunglass standards as, despite adversely affecting performance, two of the coloured sunglasses pass all national sunglass standards and one of them passes some national standards.
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| Figure 1. Response times and error rates of colour normals and deuteranopes in recognizing red, yellow and green simulated traffic signals for a range of sunglass tints. |
When Red Lights Look Yellow
Professors Wood and Atchison are investigating a phenomenon reported on the Queensland railway in which red signal lights viewed from a long distance appear yellow or white when defocused [3]. This was investigated in the field and in the laboratory. Figure 2 below shows the % of times that this occurred in the laboratory as a function of defocus for two angular subtenses. The phenomenon occurred for a limited range of positive defocus only. The optical and neural bases for this phenomenon are being explored with Dr Zele and Ms Gupta.
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| Figure 2. The percentage of times that red lights appeared yellow when defocused by different amounts for 0.7’ and 1.4’ subtenses |
To investigate the optical basis, Atchison, Zele, Guo and Gupta have manipulated the chromatic aberrations of the eye and compensated for the eye’s monochromatic aberrations. The chromatic aberration was manipulated by a Powell lens [4]. This has two components, a doublet which has similar chromatic aberration to that of eyes, and a triplet which has the reverse chromatic aberration to that of the eye. The complete Powell lens compensates for the eye’s chromatic aberration (Figure 3). The eye’s higher order monochromatic aberrations were compensated using an adaptive optics system.
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| Figure 3. Mean longitudinal chromatic aberration of 7 subjects with the Powell lens and its components. |
Figure 4 shows that without an additional lens and with or without adaptive optics correction, participants observed the phenomenon with about +0.5 D defocus. It was also observed with the doublet in the positive direction and was more obvious. When the eye’s chromatic aberrations were minimized with the Powell lens, the appearance of the red light did not change. The triplet lens reversed the direction in which the phenomenon could be seen.
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| Figure 4. Defocus producing the red light phenomenon under different conditions (4mm pupils). Error bars represent standard deviations of the subject group. |
Thus, the phenomenon is related to the presence and magnitude of longitudinal chromatic aberration, but is not related to monochromatic aberrations.
References
- Atchison DA, Pedersen CA, Dain SJ, Wood JM (2003). Traffic signal colour recognition is a problem for both protan and deutan colour vision deficients. Human Factors 45, 495-503.
- Dain SJ, Wood JM, Atchison DA. Sunglasses and traffic signal recognition and detection by color deficients. Submitted to Optom Vis Sci.
- Wood JM, Atchison DA, Chaparro A (2005). When red lights look yellow. Invest Ophthalmol Vis Sci 45, 4348-4352.
- Atchison DA, Smith G (2000). Optics of the human eye. Butterworth-Heinemann, Oxford, 189.