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Non-degenerate two-photon absorption (NTA) offers an attractive route for wide-field mid-infrared imaging by mapping long wavelength information into the spectral detection windows of mature near-infrared detector technologies. However, existing NTA implementations rely almost exclusively on complex, large-footprint femtosecond laser systems, severely limiting practicality and scalability. Here, we demonstrate an NTA imaging platform that replaces the ultrafast laser with a compact nanosecond mid-IR source coupled to a high-definition indium gallium arsenide camera. Operating in the nanosecond regime removes stringent temporal-overlap requirements, dramatically simplifying system architecture while preserving high detection sensitivity. Using this approach, we achieve chemically selective, wide-field imaging deep into the mid-IR molecular fingerprint region and demonstrate, for the first time, video-rate NTA imaging in this spectrally rich regime. By combining relaxed alignment constraints, compact excitation, and high-speed fingerprint-region imaging, this work establishes nanosecond NTA as a practical and scalable foundation for next-generation mid-IR chemical imaging. 

Single-shot 3D optical microscopy that can capture high-resolution information over a large volume has broad applications in biology. Existing 3D imaging methods using point-spread-function (PSF) engineering often have limited depth of field (DOF) or require custom and often complex design of phase masks. We propose a new, to the best of our knowledge, PSF approach that is easy to implement and offers a large DOF. The PSF appears to be axially V-shaped, engineered by replacing the conventional tube lens with a pair of axicon lenses behind the objective lens of a wide-field microscope. The 3D information can be reconstructed from a single-shot image using a deep neural network. Simulations in a 10× magnification wide-field microscope show the V-shaped PSF offers excellent 3D resolution (<2.5 µm lateral and ∼15 µm axial) over a ∼350 µm DOF at a 550 nm wavelength. Compared to other popular PSFs designed for 3D imaging, the V-shaped PSF is simple to deploy and provides high 3D reconstruction quality over an extended DOF. 

We propose a V-shape PSF generated from double axicon lenses in the collection path of wide-field microscopes for 3D high-resolution imaging with an extended depth of field.