Edge processing by synthetic aperture superresolution in digital holographic microscopy

Optimal modified lateral shearing interferometer with axial range extension by using a dual optical plate

We present a method to extend the axial range of digital holographic microscopy based on the optimal modified lateral shearing interferometer (MLSI). The proposed system can extend the axial range by using a dual optical plate. The interference pattern with two spatial wavelengths is generated by the plate with different thicknesses. These spatial wavelengths transfer a dual spatial frequency into the Fourier plane by using FFT. Two phases are extracted by a dual spatial frequency and combined to create a synthetic wavelength, which is applied to measure the micrometer-scale object without phase unwrapping. Also, the noise-reducing algorithm is used to reduce phase noise caused by the amplified noise of the synthetic wavelength. The experimental result confirms the feasibility of the optimal MLSI by using a dual optical plate.

Portable lensless wide-field microscopy imaging platform based on digital inline holography and multi-frame pixel super-resolution

In this paper, an irregular displacement-based lensless wide-field microscopy imaging platform is presented by combining digital in-line holography and computational pixel super-resolution using multi-frame processing. The samples are illuminated by a nearly coherent illumination system, where the hologram shadows are projected into a complementary metal-oxide semiconductor-based imaging sensor. To increase the resolution, a multi-frame pixel resolution approach is employed to produce a single holographic image from multiple frame observations of the scene, with small planar displacements. Displacements are resolved by a hybrid approach: (i) alignment of the LR images by a fast feature-based registration method, and (ii) fine adjustment of the sub-pixel information using a continuous optimization approach designed to find the global optimum solution. Numerical method for phase-retrieval is applied to decode the signal and reconstruct the morphological details of the analyzed sample. The presented approach was evaluated with various biological samples including sperm and platelets, whose dimensions are in the order of a few microns. The obtained results demonstrate a spatial resolution of 1.55 µm on a field-of-view of ≈30 mm².