5. Face Recognition Techniques
The method for acquiring face images depends upon the
underlying application. For instance, surveillance applications
may best be served by capturing face images by means of a
video camera while image database investigations may
require static intensity images taken by a standard camera.
Some other applications, such as access to top security
domains, may even necessitate the forgoing of the nonintrusive
quality of face recognition by requiring the user
to stand in front of a 3D scanner or an infra-red sensor.
Therefore, depending on the face data acquisition methodology,
face recognition techniques can be broadly divided
into three categories: methods that operate on intensity
images, those that deal with video sequences, and those
that require other sensory data such as 3D information or
infra-red imagery. The following discussion sheds some
light on the methods in each category and attempts to give
an idea of some of the benefits and drawbacks of the
schemes mentioned therein in general (for detailed surveys,please see [44, 45]).