Nanjing University of Science and Technology has made new progress in the field of programmable lensless holographic cameras

Recently, Professor Chen Qian and Professor Zuo Chao's research group from the School of Electronic Engineering and Optoelectronic Technology at Nanjing University of Science and Technology proposed a minimalist optical imaging method based on programmable masks - programmable Fresnel zone aperture lensless imaging technology. The related achievement, titled "Lensless Imaging with a Programmable Fresnel Zone Aperture," was published in the top international journal Science Advances. Zhang Xu, a master's student from the School of Optoelectronics at Nanjing University of Science and Technology in 2022, and Wang Bowen, a doctoral student from the School of Optoelectronics in 2019, are co first authors. Professor Chen Qian and Professor Zuo Chao are co corresponding authors, and they are the first completion unit and communication unit.

Traditional optical imaging systems mainly rely on the collaborative cooperation between image sensors and optical lenses to achieve the recording and focusing of optical signals separately. In recent years, with the rapid development of applications such as mobile photography and wearable devices, image sensors have achieved miniaturization and low cost, basically meeting the needs of most application scenarios for lightweight and economy. However, optical lenses, especially high-performance lenses, still face problems such as large size, heavy weight, and high manufacturing costs, which seriously restrict the application of imaging systems in scenarios with high lightweight requirements such as virtual reality (VR), augmented reality (AR), and human-computer interaction. This has become a key bottleneck that currently restricts the overall performance improvement and application expansion of the system.

Lens free imaging technology introduces a front-end optical encoding mask to replace traditional lens control of the light field, and combines back-end digital computing to demodulate the light field information, effectively reducing the cost and volume of traditional optical imaging systems, and achieving high-dimensional perception and phase inversion of incoherent light fields. However, existing static masks have fixed mask structures and system parameters that are difficult to flexibly adjust according to scene requirements, which makes the system prone to aliasing artifacts, reconstruction pathology, and other problems under complex or non ideal conditions, affecting imaging quality and usability. Therefore, how to further improve system resolution, signal-to-noise ratio, and enhance adaptability to complex dynamic scenes while maintaining the basic architecture of "minimalist optics" for lensless imaging is a core issue and technical challenge that urgently needs to be overcome in this field.

To address the aforementioned issues, the research team innovatively introduced the concept of "encoding regulation" and proposed a minimalist optical imaging technique based on "programmable masks" - the LenslessImaging with a Programmable Fresnel Zone Aperture (FZA) lensless imaging method (LIP). By dynamically displaying FZA patterns with spatial offset on programmable masks, LIP can achieve sub aperture information modulation and acquisition in the frequency domain, and fuse the data of each sub aperture using parallel reconstruction algorithms to obtain high-resolution, high signal-to-noise ratio lensless holographic images (Figure 1).

Figure 1. Schematic diagram of programmable FZA lensless holographic imaging system. (A) Composition and schematic diagram of imaging system; (B) Lens free imaging framework and encoding control strategy based on joint optimization of spatial and frequency domains; (C) Small scale LIP lensless imaging module independently developed by the team

Source: opticsky