High-Resolution, Lightweight Remote Sensing via Harmonic Diffractive Optical Imaging Systems and Deep Denoiser Prior Image Restoration

The weight of traditional space optical imaging systems often increases nearly cubically with the increase in aperture size. To overcome this limitation, this study proposes the use of a lightweight harmonic diffractive optical imaging system combined with deep denoiser prior image restoration, to achieve high-resolution, lightweight remote sensing. This research first designed a novel 150-order harmonic diffractive optical element (H-DOE) featuring a 40-mm aperture size and a 320-mm focal length, which is equipped with seven annular zones covering a broad spectral band (500–800 nm). Its slim structure significantly reduces weight and volume, thereby lowering its launch costs. Furthermore, to address the blurring issues encountered in H-DOE imaging tasks and attain enhanced image resolution, this study incorporates an advanced image restoration technique. This technique employs a deep denoiser as a prior module, which is embedded into a model-based image restoration optimization framework. The newly trained deep denoiser utilizes a U-Net architecture integrating a transformer and residual structures and is adept at handling complex noise during the optical imaging process. The experimental results demonstrate that the performance of the proposed image restoration strategy based on a deep denoiser surpasses that of the existing technologies, elevating the resolvable frequency of the modulation transfer function (MTF) of an H-DOE imaging system from 40.58 to 98.55 lp/mm, an enhancement of 142.9%. This significant image quality improvement showcases its vast potential for use in future high-resolution, lightweight remote sensing applications.

I. Introduction

With the continuous advancement of global remote sensing technology, enhancing the resolutions of spatial imaging platforms is considered fundamental to the development of Earth observation technology. High-resolution optical remote sensing satellites play crucial roles in the environmental monitoring, disaster response, urban planning, and national security domains [1], [2], [3], [4], [5]. Nevertheless, improving the spatial resolutions of optical remote sensing systems imposes inherent challenges due to physical limitations, particularly the size and mass constraints of satellite platforms. The weight of traditional space optical imaging systems often increases nearly cubically with the increase in aperture size [6], [7]. These space optical imaging systems are critical for capturing high-quality images, yet their weights and volumes are strictly limited due to the capacity constraints of launch vehicles, which can impact launch costs. Moreover, optical systems, including their apertures, focal lengths, and overall architectures, must be designed within these constraints, often at the expense of sacrificing potential resolution enhancements [8], [9], [10], [11].