# Adaptive pixel-super-resolved lensfree holography for wide-field on-chip microscopy

## TL;DR

This paper introduces an adaptive pixel-super-resolved lensfree holography method that significantly improves resolution and SNR in wide-field on-chip microscopy without complex hardware modifications.

## Contribution

The proposed APLI method addresses pixel aliasing through Z-scanning and introduces error correction and adaptive strategies, enhancing image quality beyond traditional limits.

## Key findings

- Achieved 770 nm lateral resolution surpassing the Nyquist limit
- Full-FOV reconstruction of a USAF resolution target
- Demonstrated potential in biological imaging applications

## Abstract

High-resolution wide field-of-view (FOV) microscopic imaging plays an essential role in various fields of biomedicine, engineering, and physical sciences. As an alternative to conventional lens-based scanning techniques, lensfree holography provides a new way to effectively bypass the intrinsical trade-off between the spatial resolution and FOV of conventional microscopes. Unfortunately, due to the limited sensor pixel-size, unpredictable disturbance during image acquisition, and sub-optimum solution to the phase retrieval problem, typical lensfree microscopes only produce compromised imaging quality in terms of lateral resolution and signal-to-noise ratio (SNR). Here, we propose an adaptive pixel-super-resolved lensfree imaging (APLI) method which can solve, or at least partially alleviate these limitations. Our approach addresses the pixel aliasing problem by Z-scanning only, without resorting to subpixel shifting or beam-angle manipulation. Automatic positional error correction algorithm and adaptive relaxation strategy are introduced to enhance the robustness and SNR of reconstruction significantly. Based on APLI, we perform full-FOV reconstruction of a USAF resolution target ($\sim$29.85 $m{m^2}$) and achieve half-pitch lateral resolution of 770 $nm$, surpassing 2.17 times of the theoretical Nyquist-Shannon sampling resolution limit imposed by the sensor pixel-size (1.67 $\mu m$). Full-FOV imaging result of a typical dicot root is also provided to demonstrate its promising potential applications in biologic imaging.