Pixel super-resolved lens-free on-chip microscopy based on dual laterally shifting modulation

Area of Science:

• Optical Imaging
• Microscopy
• Computational Imaging

Background:

• Traditional lens-based microscopy faces a trade-off between spatial resolution and field of view (FOV).
• Lens-free microscopy offers an alternative but often requires precise mechanical components, limiting stability and cost-effectiveness.
• Phase retrieval techniques are explored to overcome conventional microscopy limitations.

Purpose of the Study:

• To develop a robust, cost-effective, pixel super-resolved lens-free imaging method.
• To bypass the resolution-FOV trade-off inherent in conventional microscopy.
• To address the stability and accuracy issues associated with mechanical translation stages in lens-free systems.

Main Methods:

• A dual laterally shifting modulation technique using a thin diffuser placed between the object and image sensor.
• Simultaneous transverse scanning of the diffuser and object to introduce diversity for phase retrieval and pixel super-resolution.
• A registration algorithm to recover positional shifts, coupled with a pixel super-resolution phase-retrieval algorithm to reconstruct the object and unknown diffuser.

Main Results:

• Numerical simulations validated the proposed scheme.
• Experimental validation using a resolution target and pollen sample achieved a FOV of ~30 mm².
• A half-pitch resolution of 0.78 µm was achieved, exceeding the Nyquist-Shannon sampling limit by 2.14 times.
• 3D refocusing capability was demonstrated using a thick mosquito sample.

Conclusions:

• The proposed dual modulation lens-free imaging method offers a stable and cost-effective solution for high-resolution, wide-field imaging.
• This approach effectively overcomes the limitations of conventional microscopy and existing lens-free techniques.
• The method shows potential for diverse applications requiring high-performance imaging, including 3D reconstruction.