The optimization of image resolution for digital holographic scanning imaging of biological cells is investigated. Digital holographic scanning imaging experiments on the upper epidermal cells of onions are performed to demonstrate the validity of resolution optimization algorithm. In the experiments, the holograms of the upper epidermal cells of onion are recorded at a certain scanning rate, and then are processed by using the resolution optimization algorithm. As a result, the phase images of the onion epidermal cells with higher contrast and resolution are obtained. According to the synthetic holograms, the changes of cell nucleus and actin microfilament inside onion’s epidermal cells are displayed. In addition, the dehydration process and plasmolysis phenomenon inside onion epidermal cells are also exhibited by recording longterm scanning holograms of living epidermal cells. The experimental results demonstrate that image quality of living onion epidermal cells can be improved by optimizing the algorithms.
A method for measuring the channel size of microfluidic chip by using optical coherence tomography (OCT) is investigated. Based on spectral-domain OCT imaging and image processing, an OCT system for measurement of the microfluidic channel size is developed, which is suitable for planar two-dimensional measurement. The cross-sectional images of the micro-channel of a microfluidic chip are obtained by using OCT continuous B-scan technology. With image processing for the acquired image in noise elimination and dispersion compensation, the size of the micro-channels in depth is achieved. Comparing with the single-scan OCT imaging mode, back-passing multiple-scans mode has the capability of high image quality to achieve high measurement precision of micro-channel size.
KEYWORDS: Holograms, Digital holography, 3D image reconstruction, Image resolution, Reconstruction algorithms, Digital imaging, Detection and tracking algorithms, Phase shifts, Spatial resolution, Signal to noise ratio
In this paper, the method of recognition and superposition of sub-pixel shifting in digital holograms is investigated. A group of non-scanning holograms is recognized and superposed by using sub-pixel shifting algorithm. Further, spatio-temporal scanning holograms with sub-pixel displacement are recognized and superposed to further improve imaging resolution by combining spatio-temporal scanning digital holography with sub-pixel shifting algorithm. The experimental results verify the feasibility of improving resolution with sub-pixel displacement.
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