Triple Consistency for Transparent Cheating Problem in Light Field Depth Estimation

Depth estimation extracting scenes' structural information is a key step in various light field(LF) applications. However, most existing depth estimation methods are based on the Lambertian assumption, which limits the application in non-Lambertian scenes. In this paper, we discover a unique transparent cheating problem for non-Lambertian scenes which can effectively spoof depth estimation algorithms based on photo consistency. It arises because the spatial consistency and the linear structure superimposed on the epipolar plane image form new spurious lines. Therefore, we propose centrifugal consistency and centripetal consistency for separating the depth information of multi-layer scenes and correcting the error due to the transparent cheating problem, respectively. By comparing the distributional characteristics and the number of minimal values of photo consistency and centrifugal consistency, non-Lambertian regions can be efficiently identified and initial depth estimates obtained. Then centripetal consistency is exploited to reject the projection from different layers and to address transparent cheating. By assigning decreasing weights radiating outward from the central view, pixels with a concentration of colors close to the central viewpoint are considered more significant. The problem of underestimating the depth of background caused by transparent cheating is effectively solved and corrected. Experiments on synthetic and real-world data show that our method can produce high-quality depth estimation under the transparency and the reflectivity of 90% to 20%. The proposed triple-consistency-based algorithm outperforms state-of-the-art LF depth estimation methods in terms of accuracy and robustness.