The pose problem is one of the bottlenecks in automatic face recognition. We argue that one of the diffculties in this problem is the severe misalignment in face images or feature vectors with different poses. In this paper, we propose that this problem can be statistically solved or at least mitigated by maximizing the intra-subject across-pose correlations via canonical correlation analysis (CCA). In our method, based on the data set with coupled face images of the same identities and across two different poses, CCA learns simultaneously two linear transforms, each for one pose. In the transformed subspace, the intra-subject correlations between the different poses are maximized, which implies pose-invariance or pose-robustness is achieved. The experimental results show that our approach could considerably improve the recognition performance. And if further enhanced with holistic+local feature representation, the performance could be comparable to the state-of-the-art.
Besides the geometrical approaches, building statistical models is another popular way to recognize faces across poses. Hitherto, a typical statistical approach is the eigen light-field method proposed by @cite_6 . They built a complete appearance model including all possible pose variations. A test image can be viewed as a part of this complete model. The missing parts are estimated from the available parts. The recognition is performed by comparing the coefficients of the complete appearance model. The tied factor analysis method proposed by @cite_49 is another typical statistical approach. In this method some tied factors across pose difference are learned using Expectation Maximization algorithm. Then, face recognition is performed based on the probabilistic distance metric that built on the factor loadings. Besides principal component analysis and factor analysis, @cite_17 Sharma and Jacobs @cite_28 applied partial least squares in cross-pose face recognition. They used partial least squares to learn a pair of projection matrix for two different poses, and cross-pose face recognition is performed by comparing the intermediate correlated projections''.
@cite_28 @cite_49 @cite_6 @cite_17
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This paper presents a novel way to perform multi-modal face recognition. We use Partial Least Squares (PLS) to linearly map images in different modalities to a common linear subspace in which they are highly correlated. PLS has been previously used effectively for feature selection in face recognition. We show both theoretically and experimentally that PLS can be used effectively across modalities. We also formulate a generic intermediate subspace comparison framework for multi-modal recognition. Surprisingly, we achieve high performance using only pixel intensities as features. We experimentally demonstrate the highest published recognition rates on the pose variations in the PIE data set, and also show that PLS can be used to compare sketches to photos, and to compare images taken at different resolutions. Face recognition algorithms perform very unreliably when the pose of the probe face is different from the gallery face: typical feature vectors vary more with pose than with identity. We propose a generative model that creates a one-to-many mapping from an idealized "identity" space to the observed data space. In identity space, the representation for each individual does not vary with pose. We model the measured feature vector as being generated by a pose-contingent linear transformation of the identity variable in the presence of Gaussian noise. We term this model "tied" factor analysis. The choice of linear transformation (factors) depends on the pose, but the loadings are constant (tied) for a given individual. We use the EM algorithm to estimate the linear transformations and the noise parameters from training data. We propose a probabilistic distance metric that allows a full posterior over possible matches to be established. We introduce a novel feature extraction process and investigate recognition performance by using the FERET, XM2VTS, and PIE databases. Recognition performance compares favorably with contemporary approaches. Arguably the most important decision to be made when developing an object recognition algorithm is selecting the scene measurements or features on which to base the algorithm. In appearance-based object recognition, the features are chosen to be the pixel intensity values in an image of the object. These pixel intensities correspond directly to the radiance of light emitted from the object along certain rays in space. The set of all such radiance values over all possible rays is known as the plenoptic function or light-field. In this paper, we develop a theory of appearance-based object recognition from light-fields. This theory leads directly to an algorithm for face recognition across pose that uses as many images of the face as are available, from one upwards. All of the pixels, whichever image they come from, are treated equally and used to estimate the (eigen) light-field of the object. The eigen light-field is then used as the set of features on which to base recognition, analogously to how the pixel intensities are used in appearance-based face and object recognition. The pose problem is one of the bottlenecks for face recognition. In this paper we propose a novel cross-pose face recognition method based on partial least squares (PLS). By training on the coupled face images of the same identities and across two different poses, PLS maximizes the squares of the intra-individual correlations. Therefore, it leads to improvements in recognizing faces across pose differences. The experimental results demonstrate the effectiveness of the proposed method.