Unsupervised domain adaptation methods have been proposed to tackle the problem of covariate shift by minimizing the distribution discrepancy between the feature embeddings of source domain and target domain. However, the standard evaluation protocols assume that the conditional label distributions of the two domains are invariant, which is usually not consistent with the real-world scenarios such as long-tailed distribution of visual categories. In this article, the imbalanced domain adaptation (IDA) is formulated for a more realistic scenario where both label shift and covariate shift occur between the two domains. Theoretically, when label shift exists, aligning the marginal distributions may result in negative transfer. Therefore, a novel cluster-level discrepancy minimization (CDM) is developed. CDM proposes cross-domain similarity learning to learn tight and discriminative clusters, which are utilized for both feature-level and distribution-level discrepancy minimization, palliating the negative effect of label shift during domain transfer. Theoretical justifications further demonstrate that CDM minimizes the target risk in a progressive manner. To corroborate the effectiveness of CDM, we propose two evaluation protocols according to the real-world situation and benchmark existing domain adaptation approaches. Extensive experiments demonstrate that negative transfer does occur due to label shift, while our approach achieves significant improvement on imbalanced datasets, including Office-31, Image-CLEF, and Office-Home.

Deep learning has achieved remarkable success in numerous computer vision tasks. However, recent research reveals that deep neural networks are vulnerable to natural perturbations from poor visibility conditions, limiting their practical applications. While several studies have focused on enhancing model robustness in poor visibility conditions through techniques such as image restoration, data augmentation, and unsupervised domain adaptation, these efforts are predominantly confined to specific scenarios and fail to address multiple poor visibility scenarios encountered in real-world settings. Furthermore, the valuable prior knowledge inherent in poor visibility images is seldom utilized to aid in resolving high-level computer vision tasks. In light of these challenges, we propose a novel deep learning paradigm designed to bolster the robustness of object recognition across diverse poor visibility scenes. By observing the prior information in diverse poor visibility scenes, we integrate a feature matching module based on this prior knowledge into our proposed learning paradigm, aiming to facilitate deep models in learning more robust generic features at shallow levels. Moreover, to further enhance the robustness of deep features, we employ an adversarial learning strategy based on mutual information. This strategy combines the feature matching module to extract task-specific representations from low visibility scenes in a more robust manner, thereby enhancing the robustness of object recognition. We evaluate our approach on self-constructed datasets containing diverse poor visibility scenes, including visual blur, fog, rain, snow, and low illuminance. Extensive experiments demonstrate that our proposed method yields significant improvements over existing solutions across various poor visibility conditions.

Three of the most viable glasses-free 3D display methods were chosen for our research at NTU's Advanced Displays Laboratory. Our multi-layer light field display enables a smaller form factor, and faster algorithms combined with horizontal parallax-only speed-up Tensor Display computation time; a spin-off from this is an augmented reality light field near-eye display with focus cues. Head tracked displays use a directional backlit liquid crystal display panel to produce multiple sets of exit pupil pairs that employ a head tracker to follow the users' eyes. This enables a ‘plug and play solution’ where existing content can be used without resolution loss. We have developed three different spatio-temporally multiplexed super multiview display systems based on liquid crystal displays, organic light emitting diodes and fast projectors. In this paper, the background, status of the prototypes and their performance is explained, and the future direction of our research is described.

The recent emergence of light field technology has led to new opportunities for immersive visual communication that has a need for high spatial and angular resolution, both of which contribute to a large image storage footprint and high-latency transmission. Task-driven downsampling methods have been proposed as a solution, and have shown improvements in single-image restoration. However, they are inevitable to disregard light field's intrinsic properties in the corresponding tasks. In this paper, we propose a light-field-specific task-driven downsampling framework, called the LFCrNet. The LFCrNet operates on a learning-based decreasing and increasing resolution in an end-to-end manner in order to utilize a cross-view asymmetric sampling technique. In detail, it separates raw data into disparity and non-disparity patterns by measuring pixel-wise residuals between the sub-aperture central view and auxiliary views. Then, a chain of three-dimensional (3-D) deformable residual blocks (DRBs) is used to extract disparity features and manage these features regard of their intrinsic property individually. Afterwards, they are compacted into spatio-angular domains through a 3-D deformable downsampler (3-DDS). The non-disparity information is integrated into a separate pipeline that leverages spatial similarity across multiple light field views. This technique is capable of preserving specific occlusion components, and subsequently, restoring them using a learning-based upscaling method to generate a high-quality reconstruction. In general, our method has shown superior performance on multiple open-source datasets by a significant margin.

Precise segmentation of brain tumors, particularly contrast-enhancing regions visible in post-contrast MRI (areas highlighted by contrast agent injection), is crucial for accurate clinical diagnosis and treatment planning but remains challenging. However, current methods exhibit notable performance degradation in segmenting these enhancing brain tumor areas, largely due to insufficient consideration of MRI-specific tumor features such as complex textures and directional variations. To address this, we propose the Harmonized Frequency Fusion Network (HFF-Net), which rethinks brain tumor segmentation from a frequency-domain perspective. To comprehensively characterize tumor regions, we develop a Frequency Domain Decomposition (FDD) module that separates MRI images into low-frequency components, capturing smooth tumor contours and high-frequency components, highlighting detailed textures and directional edges. To further enhance sensitivity to tumor boundaries, we introduce an Adaptive Laplacian Convolution (ALC) module that adaptively emphasizes critical high-frequency details using dynamically updated convolution kernels. To effectively fuse tumor features across multiple scales, we design a Frequency Domain Cross-Attention (FDCA) integrating semantic, positional, and slice-specific information. We further validate and interpret frequency-domain improvements through visualization, theoretical reasoning, and experimental analyses. Extensive experiments on four public datasets demonstrate that HFF-Net achieves an average relative improvement of 4.48\% (ranging from 2.39\% to 7.72\%) in the mean Dice scores across the three major subregions, and an average relative improvement of 7.33% (ranging from 5.96% to 8.64%) in the segmentation of contrast-enhancing tumor regions, while maintaining favorable computational efficiency and clinical applicability. Code: https://github.com/VinyehShaw/HFF.