Near-infrared holography extends lensless microscopy into thicker tissue

Researchers at Warsaw University of Technology say near-infrared illumination and a larger sample-sensor gap let lensless holographic microscopy recover detail through tissue-like scattering layers far thicker than visible light can handle. The study, published in Opto-Electronic Advances on Sept. 20, 2026, points to a faster, wider-field way to image thick biological samples without lenses or labels.

Why it matters: - Lensless holographic microscopy has been limited to thin, weakly scattering samples because strong scattering destroys the interference pattern it needs to reconstruct an image. - The new approach extends that method into the multiple-scattering regime, opening a path to wider-field imaging of thick biological tissue with simpler hardware. - The work also shows that ordinary silicon sensors can still support near-infrared holography at very low sensitivity, which could reduce the need for specialized infrared components.

What happened: - Researchers at Warsaw University of Technology tested lensless digital holographic microscopy across six wavelengths from 480 to 1100 nm. - The study used tissue-mimicking milk layers and calibrated targets to measure how much detail remained recoverable as scattering increased. - The results were published online in Opto-Electronic Advances on Sept. 20, 2026. - The paper is titled "Near-infrared lensless holographic microscopy on a standard sensor for label-free mesoscale imaging in multiple scattering." - The DOI is 10.29026/oea.2026.260088.

The details: - At visible wavelengths, the system became fully unresolved once scattering-layer thickness reached 180 to 360 µm, depending on wavelength. - At 1100 nm, resolvable features survived through about 1.4 mm of tissue-like medium. - That depth is nearly four times greater than the thickness reached at 632 nm. - The team used a standard CMOS sensor, even though its quantum efficiency at 1100 nm was only 0.19%. - The lensless setup delivered a field of view of about 116 mm2 without raster scanning or image stitching. - Increasing the sample-sensor distance from about 3 mm to 12 mm improved lateral resolution from roughly 11 µm to 5.5 µm. - The team says the longer propagation distance lets diffuse background spread faster than the useful interference signal, making fringes easier to detect. - At 1100 nm, the system produced label-free amplitude and phase images of uncleared mouse liver sections up to 60 µm thick and brain sections up to 250 µm thick. - The study was led by first author Dr. Emilia Wdowiak, with collaborators from the Nencki Institute of Experimental Biology, the Medical University of Warsaw, the Maria Sklodowska-Curie National Research Institute of Oncology, and the Centre of Postgraduate Medical Education. - The research was supported by Poland's National Centre for Research and Development through the LIDER XIV programme. - Equipment was co-funded by the Warsaw University of Technology Excellence Initiative: Research University program.

Between the lines: - The key advance is not a new microscope body, but a new operating regime for an existing one. - Near-infrared light preserves more usable information in scattering media, and lensless imaging can exploit that with a standard sensor architecture. - The finding that larger sample-sensor gaps can improve resolution runs against a common rule in lensless imaging and suggests geometry should be tuned for scattering conditions, not just minimized. - The work stays in the in vitro and ex vivo lane; it does not claim deep imaging inside living tissue.

What's next: - The team says future work could combine distance-aware acquisition with scattering-aware or physics-informed reconstruction. - More sensitive detectors could further improve performance in low-photon conditions. - The approach could support faster tissue survey, computational imaging through complex media, and compact instruments for labs that need scalable imaging systems.

The bottom line: - Near-infrared lensless holography on a standard sensor can push label-free microscopy much deeper into scattering tissue than visible light, while preserving the wide field and simplicity that make the method attractive.