Robust Focus Volume Regularization in Shape From Focus

• Published in: IEEE transactions on image processing 2021, Vol.30, p.7215-7227
• Main Authors: Ali, Usman, Mahmood, Muhammad Tariq
• Format: Article
• Language: English
• Subjects: Algorithms; Cameras; Convergence; depth map; focus measure; Frequency modulation; Image quality; Image reconstruction; Image sequences; non-convex optimization; Optimization; Regularization; Robustness; Sequences; Shape; Shape from focus (SFF); Shape recognition; Solution space; Three-dimensional displays; volume regularization
• ISSN: 1057-7149; 1941-0042
• DOI: 10.1109/TIP.2021.3100268

Shape from focus (SFF) reconstructs 3D shape of the scene from a sequence of multi-focus images, and the quality of reconstructed shape mainly depends on the accuracy of image focus volume (FV). Traditional SFF techniques exhibit poor performance in preserving structural edges and fine details while removing noisy artifacts, and mostly they do not incorporate any additional shape prior. Therefore, in this paper, we propose to refine FV by formulating an energy minimization framework that employs a nonconvex regularizer and incorporates two types of shape priors. The proposed regularizer is robust against noisy focus values. The first proposed shape prior is input image sequence and it is a single and static shape prior. While, the second shape prior corresponds to a series of shape priors. These shape priors are FVs which are iteratively obtained on-the-fly. Both of these shape priors constrain the solution space for output FV. We optimize nonconvex energy function through majorize-minimization algorithm which iteratively guarantees a local minimum and converges quickly. Experiments have been conducted to evaluate accuracy and convergence properties of the proposed method. Experimental results of synthetic and real image sequences demonstrate that our method achieves superior results in terms of ability to reconstruct accurate 3D shapes as compared to existing approaches.