Resampling and super-resolution of hexagonally sampled images using deep learning

TL;DR

This paper introduces a deep learning-based super-resolution system that enhances hexagonally sampled images by converting them to rectangular grids and applying a CNN, demonstrating advantages over traditional methods.

Contribution

The paper presents a novel SR approach for hexagonally sampled images using non-uniform interpolation and RCAN, highlighting practical benefits of hexagonal sampling with modern CNN techniques.

Findings

Hexagonal sampling combined with RCAN outperforms direct application on rectangular samples.

The system effectively accounts for optical and sensor degradations.

Hexagonal sampling shows practical advantages in super-resolution tasks.

Abstract

Super-resolution (SR) aims to increase the resolution of imagery. Applications include security, medical imaging, and object recognition. We propose a deep learning-based SR system that takes a hexagonally sampled low-resolution image as an input and generates a rectangularly sampled SR image as an output. For training and testing, we use a realistic observation model that includes optical degradation from diffraction and sensor degradation from detector integration. Our SR approach first uses non-uniform interpolation to partially upsample the observed hexagonal imagery and convert it to a rectangular grid. We then leverage a state-of-the-art convolutional neural network (CNN) architecture designed for SR known as Residual Channel Attention Network (RCAN). In particular, we use RCAN to further upsample and restore the imagery to produce the final SR image estimate. We demonstrate that this system is superior to applying RCAN directly to rectangularly sampled LR imagery with equivalent sample density. The theoretical advantages of hexagonal sampling are well known. However, to the best of our knowledge, the practical benefit of hexagonal sampling in light of modern processing techniques such as RCAN SR is heretofore untested. Our SR system demonstrates a notable advantage of hexagonally sampled imagery when employing a modified RCAN for hexagonal SR.