Nonmechanical parfocal and autofocus features based on wave propagation distribution in lensfree holographic microscopy

Abstract

Performing long-term cell observations is a non-trivial task for conventional optical microscopy, since it is usually not compatible with environments of an incubator and its temperature and humidity requirements. Lensless holographic microscopy, being entirely based on semiconductor chips without lenses and without any moving parts, has proven to be a very interesting alternative to conventional microscopy. Here, we report on the integration of a computational parfocal feature, which operates based on wave propagation distribution analysis, to perform a fast autofocusing process. This unique non-mechanical focusing approach was implemented to keep the imaged object staying in-focus during continuous long-term and real-time recordings. A light-emitting diode (LED) combined with pinhole setup was used to realize a point light source, leading to a resolution down to 2.76 μm. Our approach delivers not only in-focus sharp images of dynamic cells, but also three-dimensional (3D) information on their (x, y, z)-positions. System reliability tests were conducted inside a sealed incubator to monitor cultures of three different biological living cells (i.e., MIN6, neuroblastoma (SH-SY5Y), and Prorocentrum minimum). Altogether, this autofocusing framework enables new opportunities for highly integrated microscopic imaging and dynamic tracking of moving objects in harsh environments with large sample areas.

DWT-SVD Based Watermarking for High-Resolution Medical Holographic Images

“…With its advantages such as wide field of view, high spatial resolution, easy integration, and low cost, DIHM has become a tool that performs essential functions, especially in the laboratory and clinical stages of medical imaging. DIHM is used in laboratory conditions to imaging microorganisms such as cancer cells, bacteria, yeast cells, or sperm cells, perform viability analyses, track the cells in 2D, and determine sample 3D localizations [38][39][40][41][42]. It is used in the clinic for human-level counting and classifying blood cells, morphological examination of medical samples, and disease diagnosis [43][44][45].…”

“…e interaction of the beams emitted from the light source with the sample and the diffraction patterns resulting from this interaction are recorded via charge-coupled devices (CCD) or complementary metal oxide semiconductors (CMOS) [49]. Coherent sources are used as light sources, and spatially filtered light-emitting diodes (LED) are used in many applications in the literature [38,50]. DIHM, in which no optical lens is used, uses Fourier optics' principles numerically in its image creation processes.…”

A precise bare simulation approach to the minimization of some distances. Foundations

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“…Yang et al [412], Loia & Vaccaro [230], Wood et al [394], Xu et al [404]). Another important special case of ( 112) to (114) is the omnipresent L 2 −minimization; indeed, with the choices…”