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T-Space at The University of Toronto Libraries >
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Please use this identifier to cite or link to this item: http://hdl.handle.net/1807/32773

Title: Two- and Three-dimensional Face Recognition under Expression Variation
Authors: Mohammadzade, Narges Hoda
Advisor: Hatzinakos, Dimitrios
Department: Electrical and Computer Engineering
Keywords: face recognition
3D face recognition
facial expression
point correspondence
discriminant methods
surface normal vector
3D face registration
iterative closest normal point
linear discriminant analysis
expression transformation
expression subspace
principal component analysis
biometrics
verification
generic training
single sample
expression variation
Face Recognition Grand Challenge Database
FRGC
nose detection
3D face segmentation
Issue Date: 30-Aug-2012
Abstract: In this thesis, the expression variation problem in two-dimensional (2D) and three-dimensional (3D) face recognition is tackled. While discriminant analysis (DA) methods are effective solutions for recognizing expression-variant 2D face images, they are not directly applicable when only a single sample image per subject is available. This problem is addressed in this thesis by introducing expression subspaces which can be used for synthesizing new expression images from subjects with only one sample image. It is proposed that by augmenting a generic training set with the gallery and their synthesized new expression images, and then training DA methods using this new set, the face recognition performance can be significantly improved. An important advantage of the proposed method is its simplicity; the expression of an image is transformed simply by projecting it into another subspace. The above proposed solution can also be used in general pattern recognition applications. The above method can also be used in 3D face recognition where expression variation is a more serious issue. However, DA methods cannot be readily applied to 3D faces because of the lack of a proper alignment method for 3D faces. To solve this issue, a method is proposed for sampling the points of the face that correspond to the same facial features across all faces, denoted as the closest-normal points (CNPs). It is shown that the performance of the linear discriminant analysis (LDA) method, applied to such an aligned representation of 3D faces, is significantly better than the performance of the state-of-the-art methods which, rely on one-by-one registration of the probe faces to every gallery face. Furthermore, as an important finding, it is shown that the surface normal vectors of the face provide a higher level of discriminatory information rather than the coordinates of the points. In addition, the expression subspace approach is used for the recognition of 3D faces from single sample. By constructing expression subspaces from the surface normal vectors at the CNPs, the surface normal vectors of a 3D face with single sample can be synthesized under other expressions. As a result, by improving the estimation of the within-class scatter matrix using the synthesized samples, a significant improvement in the recognition performance is achieved.
URI: http://hdl.handle.net/1807/32773
Appears in Collections:Doctoral

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