Human Skin Detection Technology for Improved Security, Search and Rescue

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Color-image based systems are excellent at locating people in aerial search and rescue operations, but fall short when it comes to discerning between actual human skin and objects with similar hues. To remedy this, researchers at the Air Force Institute of Technology (AFIT) have developed a novel two-dimensional feature space which uses the spectral absorption characteristics of melanin, hemoglobin and water to better characterize human skin.

Spectral imaging systems use information from the entire electromagnetic spectrum to provide digital images with much greater information per pixel than traditional cameras.  Feature spaces in a spectral imaging system are vectors that numerically represent an object’s characteristics. The skin detection approach is described this week in Applied Optics, a journal from The Optical Society.
 
In their work, the AFIT research team used feature spaces to key in on specific constituents of human tissue by using a skin index concerned with how water and melanin’s presence in skin manifests at two different wavelengths in the near-infrared region. These changes would cut the overall cost of hyperspectral-based search and rescue systems by a factor of seven.
 
“The study represents a crossroads between physics and statistical pattern recognition,” said Michael J. Mendenhall, assistant professor, Air Force Institute of Technology, Department of Electrical and Computer Engineering, Dayton, Ohio, USA. “The features were designed based on an understanding of the physics behind skin’s spectral shape, but in such a way that the features separated skin and non-skin pixels in order to make the pattern recognition portion of the problem more effective.”
 
“After a lot of investigation into spectral properties of false alarm sources, we arrived at a simple observation that skin is more red than green, due to the melanin in darker skin and oxygenated hemoglobin in lighter skin, whereas many of the false alarm sources were more green than red,” Mendenhall said.

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