Tim Wallace
Is that dress blue and black or white and gold? How we perceive colour is complex, influenced greatly by lighting conditions. For machines, it’s even harder to replicate the adjustments our brains make for changes in the colour of light. It’s the reason your average digital camera has settings for shooting outdoors in sunny or overcast conditions, or indoors under fluorescent or tungsten lighting.
In future, though, cameras may achieve more accurate colour sensing thanks to visionary technology inspired by the abilities of honeybees.
The insects, whose survival depends on visual identification of food sources, manage to achieve with their relatively simple brains what traditional models of human colour perception have concluded requires complex neural structures: achieving colour constancy.
So how do honeybees perceive the same colours on visited flowers, despite continuous and rapid changes in ambient illumination and background colour? The answer, according to researchers from Australian institutions, involves the three extra eyes (ocelli) the bees have on the top of their head, which look directly at the sky and contain two colour receptors attuned to sense the colour of ambient light.
While the purpose of the ocelli has been traditionally regarded as serving flight-oriented processes, the researchers report in their paper published in Proceedings of the National Academy of Sciences that their mapping of the bee’s neural tracings shows information from the ocelli feeds into the key-colour processing areas of the bee brain and is integrated with information from the insect’s two main compound eyes that directly sense flower colours.
This enables the bee’s visual system “to use a priori knowledge of the general spectral characteristics of the illuminant to achieve colour constancy based on either top-down mechanisms or local processing at hierarchically ‘high’ centres,” the researchers write.
The result of their research is a “biologically validated mathematical solution that we reveal can be readily implemented into artificial systems”.
Adrian Dyer, of RMIT University, who co-ordinated the research project involving academics from RMIT, Monash University and Deakin University, all based in Melbourne, and the Australian National University in Canberra, says the research demonstrates how bio-inspired solutions from nature can be used to tackle key problems in visual perception: “This discovery on colour constancy can be implemented into imaging systems to enable accurate colour interpretation.”
Paper co-author John Endler, of Deakin University, agrees, describing the discovery as “a superb solution to a classic problem and makes colour constancy computationally inexpensive”.
The research adds to advances being made in camera technology based on biomimicry.
In February, researchers from the University of Stuttgart presented a miniaturised camera inspired by the natural vision of predators such as eagles. Using “foveated imaging” the tiny camera was able to take photographs with a “high central acuity”, useful for applications such as endoscopy and optical sensors.
In January, scientists at Germany’s Fraunhofer Institute for Applied Optics and Precision Engineering announced a wafer-level camera lens inspired by insect compound eyes. At just 2 millimetres thick, the lens was partitioned into 135 tiny facets, like an insect’s, and enabled resolutions of up to 4 megapixels.
