Lensfree on-chip microscopy over a wide field-of-view using pixel super-resolution

TLDR

The spatial resolution of lensfree holographic microscopy is limited by the sensor pixel size. The study demonstrates lensfree holographic microscopy on a chip that achieves ~0.6 µm resolution (NA ≈ 0.5) over a 24 mm² field of view. Using partially coherent illumination from a ~50 µm aperture, the authors acquire low‑resolution in‑line holograms and then apply a sub‑pixel shifting super‑resolution algorithm to recover sub‑micron resolution across the entire sensor area. The pixel‑super‑resolution method successfully images patterned transparent substrates, blood smears, and Caenorhabditis elegans, confirming its effectiveness.

Abstract

We demonstrate lensfree holographic microscopy on a chip to achieve approximately 0.6 microm spatial resolution corresponding to a numerical aperture of approximately 0.5 over a large field-of-view of approximately 24 mm2. By using partially coherent illumination from a large aperture (approximately 50 microm), we acquire lower resolution lensfree in-line holograms of the objects with unit fringe magnification. For each lensfree hologram, the pixel size at the sensor chip limits the spatial resolution of the reconstructed image. To circumvent this limitation, we implement a sub-pixel shifting based super-resolution algorithm to effectively recover much higher resolution digital holograms of the objects, permitting sub-micron spatial resolution to be achieved across the entire sensor chip active area, which is also equivalent to the imaging field-of-view (24 mm2) due to unit magnification. We demonstrate the success of this pixel super-resolution approach by imaging patterned transparent substrates, blood smear samples, as well as Caenoharbditis Elegans.