Lensless in-line holographic microscope with Talbot grating illumination.

We have developed a wide field-of-view lensless in-line holographic microscope (LIHM) capable of acquiring microscopic images with a compact design. In our imaging system, a Ronchi grating was illuminated by a collimated laser beam to generate a Talbot self-imaging grating illumination on the sample, and the in-line holograms were recorded by a CMOS imaging sensor behind the sample. An iterative reconstruction algorithm was then applied to reconstruct the sample image while eliminating the twin-image background that appears in traditional in-line holography. In the algorithm, the dark areas of the illumination grating were used as a known constraint to define the sample support that led to convergence of the iteration. The whole-sample image can be acquired by laterally shifting the grating. We demonstrated the performance of our iteration algorithm and imaging system by successfully acquiring images of polystyrene microspheres with 5 μm diameter and the wing of a green lacewing.