High resolution integral holography using Fourier ptychographic approach

Symmetrical illumination based extending depth of field in Fourier ptychographic microscopy

Fourier ptychographic microscopy (FPM), simply replacing the traditional light source of a microscope with a LED array, can obtain high resolution and large field of view images simultaneously. A symmetrical LED illumination FPM is presented to improve the quality of high resolution images for defocus or thick samples in this paper. It is proven theoretically that symmetrical LED illumination had higher defocus tolerance than that of single LED illumination at first. Then, it is confirmed that symmetrical LED illumination FPM has better low-resolution images and reconstruction effect for defocus samples than that of single LED illumination by simulated and experimental results. Compared with the single illumination FPM, it is demonstrated that the depth of field of symmetrical FPM is more than doubled.

Unconventional methods of imaging: computational microscopy and compact implementations

In the past two decades or so, there has been a renaissance of optical microscopy research and development. Much work has been done in an effort to improve the resolution and sensitivity of microscopes, while at the same time to introduce new imaging modalities, and make existing imaging systems more efficient and more accessible. In this review, we look at two particular aspects of this renaissance: computational imaging techniques and compact imaging platforms. In many cases, these aspects go hand-in-hand because the use of computational techniques can simplify the demands placed on optical hardware in obtaining a desired imaging performance. In the first main section, we cover lens-based computational imaging, in particular, light-field microscopy, structured illumination, synthetic aperture, Fourier ptychography, and compressive imaging. In the second main section, we review lensfree holographic on-chip imaging, including how images are reconstructed, phase recovery techniques, and integration with smart substrates for more advanced imaging tasks. In the third main section we describe how these and other microscopy modalities have been implemented in compact and field-portable devices, often based around smartphones. Finally, we conclude with some comments about opportunities and demand for better results, and where we believe the field is heading.