Fusion of Visual and Thermal Face Recognition Techniques: A ...

component is connected based on a chain coding scheme; finally, ellipses are fitted based
on each connected component. Although face regions are not well representative, eye
blobs are well fitted. This ellipse fitting method may be helpful to reduce the search time
for detecting the eyes even in visual images.
Figure 12: Ellipse fitting demo
Detecting and tracking of face-like objects in cluttered scenes is an important
preprocessing stage of overall automatic face recognition. The goal of face detection is to
segment out face-like objects from cluttered scenes. Recent survey papers on face
detection techniques in visual images can be found in [55][56]. The detection of faces in
thermal images can be achieved by applying thresholding in which most skin areas are
covered.
Figure 13 shows a basic flow diagram of the face detection algorithm. Original
images are binarized with a statistically driven threshold and processed by morphological
(opening & closing) to reduce small blobs inside of the faces. Then the results are linked
using a Freeman chain-coding algorithm. A small number of connected components is
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