In order to realize the in situ detection of plankton and organic particles in the deep sea, we proposed a dynamic holographic microscopic imaging method based on the principle of parallel phase-shifting. We analyzed the implementation mechanism of the parallel phase-shifting holographic imaging. We designed the implementation scheme of the deep sea in situ detection system, carrying out experimental research on underwater dynamic holography. High resolution images were acquired and reconstructed using the resolution target and several biological samples. Experimental results show that local details of underwater samples can be clearly distinguished. We preliminarily verified the feasibility of the parallel phaseshifting holographic method to achieve underwater high-resolution in situ detection.
Compared with the arrayed waveguide grating (AWG) that widely used as optical wavelength multiplexers and/or demultiplexers (MUX/DMUX) in optical communication networks, AWG of low diffraction order has enormous potential of application in cases that need a large free spectrum range (FSR), to name a few, various integrated optical spectrometer, and wavelength MUX/DMUX in coarse wavelength division multiplexing (CWDM) networks. In the current paper, an investigation is conducted on S-shaped antisymmetric design scheme for low diffraction order AWG layouting. To reduce overall AWG device dimension and increase bend waveguide curvature radius uniformity, particle swarm optimization (PSO) with constrained conditions is employed to find optimized geometrical parameters which determine AWG structure. PSO algorithm could reduce by about 50.6% of the AWG dimension compared with previously reported AWG and thus PSO could be a promising optimization method when designing AWG.
The segmented planar imaging detectors have attracted intensive attention because of its superior imaging performance and structural compactness. The structure of radial SPIDER is investigated and the imaging progress is mathematically analyzed according to the Van Cittert-Zernike theorem. Due to the sparse sampling density in the frequency domain resulted from restriction of the structure, the imaging quality of SPIDER is unsatisfactory. In this paper, a reconstruction algorithm based on the compressed sensing theory is proposed to reconstruct the sparse signal from far fewer sampling density than the Nyquist–Shannon sampling criterion. The objective function, measurement matrix and sparse matrix are discussed according to the physical mechanism of SPIDER. The TV/L1 minimization and alternating direction multiplier method (ADMM) are used to obtain high-resolution images. Simulation results of image reconstruction demonstrate that the imaging resolution is improved remarkably than the original image.