Micro-endoscopes are widely used for detecting and visualizing hard-to-reach areas of the human body and for in vivo observation of animals. A micro-endoscope that can realize 3D imaging at the camera framerate could benefit various clinical and biological applications. In this work, we report the development of a compact light-field micro-endoscope (LFME) that can obtain snapshot 3D fluorescence imaging, by jointly using a single-mode fiber bundle and a small-size light-field configuration. To demonstrate the real imaging performance of our method, we put a resolution chart in different z positions and capture the z-stack images successively for reconstruction, achieving 333-μm-diameter field of view, 24 μm optimal depth of field, and up to 3.91 μm spatial resolution near the focal plane. We also test our method on a human skin tissue section and HeLa cells. Our LFME prototype provides epi-fluorescence imaging ability with a relatively small (2-mm-diameter) imaging probe, making it suitable for in vivo detection of brain activity and gastrointestinal diseases of animals.

The imaging field of view (FOV) of lensless microscope is consistent with the size of image sensor in use, enabling the observation of sample areas larger than 20 mm2. Combined with high-performance and even super-resolution phase retrieval algorithms, micron and sub-micron resolution can be achieved, ultimately realizing wide-field and high-resolution imaging performance simultaneously. However, high-throughput lensless imaging poses significant challenges in terms of rapid data acquisition and large-scale phase retrieval. Additionally, when observing biological samples over a large FOV, the focus plane often exhibits inconsistency among different regions, necessitating further parameter calibration. In this study, we propose a fast acquisition and efficient reconstruction strategy for coherent lensless imaging based on a multi-height imaging model. Multiple measurements are manually modulated using an axial translation stage and continuously captured by an image sensor, facilitating rapid data acquisition within seconds and requiring no hardware synchronization. The efficiency and accuracy of phase retrieval are enhanced through precise parameter calibration algorithms, as well as techniques such as region-wise parallel computing and region-wise auto-focusing. Experimental results demonstrate 7.4*5.5 mm2 FOV and 1.55 um half-pitch resolution imaging of human skin and lung tumor sections with region-wise focusing, requiring only a 2-s acquisition time and approximate 44-s reconstruction time. Furthermore, by incorporating the pixel super-resolution principle, the 1.10 um half-pitch imaging resolution is demonstrated in full-FOV peripheral blood smears without additional data required, beneficial to the identification of hollow shape and segmentation of blood cells.

We propose a dual-modal light-field micro-endoscopy using the single-mode fiber bundle in this work, obtaining the single-shot 3D endoscopic imaging in both the bright-field and fluorescence modes.