Pose Invariant Face Recognition via 3D Spatial Transformer Networks

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Solution Overview

Problem

Existing face recognition systems struggle with large pose variations between enrollment and probe images, particularly in real-world applications like law enforcement, where frontal mugshot images are matched with non-frontal or profile images, leading to decreased accuracy due to self-occluded regions and nuisance transformations.

Innovation Solution

The method employs 3D Spatial Transformer Networks to generate a 3D face model from input images at any pose, normalizing off-angle faces to a frontal viewpoint by masking non-visible regions and using only the stable half-face for recognition, transforming out-of-plane rotation into a 2D alignment problem suitable for convolutional neural networks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If pose synthesis or pose correction methods are used to handle pose variations, then face recognition can be performed on off-angle images, but self-occluded regions cause degradation in recognition accuracy as pose angle increases

Engineering Contradiction:
Improvepose toleranceVSAvoidrecognition accuracy
Core Design Contradiction:
Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The face image is segmented into two independent half-face images based on the pose angle. For positive pose angles, the left half-face is extracted; for negative pose angles, the right half-face is extracted. This segmentation eliminates self-occluded regions by selecting only the visible portion of the face, thereby maintaining recognition accuracy across various pose angles while improving pose tolerance.

Inventive Principle:
Principle #1Segmentation

2Loss of information

If whole face models are used for recognition, then complete face information is available, but recognition accuracy degrades at extreme pose angles due to self-occlusion

Engineering Contradiction:
Improveface information completenessVSAvoidrecognition accuracy
Core Design Contradiction:
Loss of informationVSMeasurement precision

Solution Approach 1:

The method extracts only the visible half-face region from the input image based on the estimated pose angle. By taking out and using only the relevant visible portion (left or right half-face) rather than the entire face image, the system avoids the degradation caused by self-occluded regions while still capturing sufficient discriminative information for accurate recognition.

Inventive Principle:
Principle #2Taking out (Extraction)

3Measurement precision

If traditional deep learning approaches are used, then state-of-the-art results are achieved on frontal images, but performance drops in challenging settings with pose variation and degradation

Engineering Contradiction:
Improvefrontal face recognition accuracyVSAvoidpose invariance
Core Design Contradiction:
Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The method performs preliminary pose angle estimation and half-face selection before the actual recognition process. By determining the pose angle and selecting the appropriate half-face region in advance, the system prepares the input data in a pose-invariant manner, enabling traditional deep learning approaches to maintain high accuracy across varying poses without requiring complex pose-invariant architectures.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentUS20200410210A1Pose invariant face recognition
Publication Date: 2020.12.31 CARNEGIE MELLON UNIV
  • US20200410210A1 patent drawing
  • US20200410210A1 patent drawing
  • US20200410210A1 patent drawing

AI summary

The disclosed method generates a pose invariant feature by normalizing off-angle faces to generate a pose invariant input image. Any face recognition mode can be used with this pre processing step. In this method, method, the 3D Spatial Transformer Networks is used to extract a 3D model of the face from an input at any pose.