The human eye is an amazing instrument and can accurately distinguish between the tiniest, most subtle differences in color. Where human vision excels in one area, it seems to fall short in others, such as perceiving minuscule details because of the natural limitations of human optics.
In a paper published today in The Optical Society’s new, high-impact journal Optica, a research team from the University of Stuttgart, Germany and the University of Eastern Finland, Joensuu, Finland, has harnessed the human eye‘s color-sensing strengths to give the eye the ability to distinguish between objects that differ in thickness by no more than a few nanometers—about the thickness of a cell membrane or an individual virus.
This ability to go beyond the diffraction limit of the human eye was demonstrated by teaching a small group of volunteers to identify the remarkably subtle color differences in light that has passed through thin films of titanium dioxide under highly controlled and precise lighting conditions. The result was a remarkably consistent series of tests that revealed a hitherto untapped potential, one that rivals sophisticated optics tools that can measure such minute thicknesses, such as ellipsometry.
“We were able to demonstrate that the unaided human eye is able to determine the thickness of a thin film—materials only a few nanometers thick—by simply observing the color it presents under specific lighting conditions,” said Sandy Peterhänsel, University of Stuttgart, Germany and principal author on the paper. The actual testing was conducted at the University of Eastern Finland.
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