Non-invasive single-shot recovery of point-spread function of a memory effect based scattering imaging system

Accessing the point-spread function (PSF) of a complex optical system is important for a variety of imaging applications. However, placing an invasive point source is often impractical, and estimating it blindly with multiple frames is slow and requires a complex non-linear optimization. Here, we introduce a simple single-shot method to non-invasively recover the accurate PSF of an isoplanatic imaging system, in the context of multiple light scattering. Our approach is based on the reconstruction of any unknown sparse hidden object using the autocorrelation imaging technique, followed by a deconvolution with a blur kernel derived from the statistics of a speckle pattern. A deconvolution on the camera image then retrieves the accurate PSF of the system, enabling further imaging applications. We demonstrate numerically and experimentally the effectiveness of this approach compared to previous deconvolution techniques

Reference-less complex wavefields characterization with a high-resolution wavefront sensor

Wavefront sensing is a widely-used non-interferometric, single-shot, and quantitative technique providing the spatial-phase of a beam. The phase is obtained by integrating the measured wavefront gradient. Complex and random wavefields intrinsically contain a high density of singular phase structures (optical vortices) associated with non-conservative gradients making this integration step especially delicate. Here, using a high-resolution wavefront sensor, we demonstrate experimentally a systematic approach for achieving the complete and quantitative reconstruction of complex wavefronts. Based on the Stokes' theorem, we propose an image segmentation algorithm to provide an accurate determination of the charge and location of optical vortices. This technique is expected to benefit to several fields requiring complex media characterization

Non-invasive imaging through thin scattering layers with broadband illumination

Memory-effect-based methods have been demonstrated to be feasible to observe hidden objects through thin scattering layers, even from a single-shot speckle pattern. However, most of the existing methods are performed with narrowband illumination or require point light-sources adjacent to the hidden objects as the references, to make an invasive pre-calibration of the imaging system. Here, inspired by the shift-and-add algorithm, we propose that by randomly selecting and averaging different sub-regions of the speckle patterns, an image pattern resembling the autocorrelation (we call it R-autocorrelation) of the hidden object can be extracted. By performing numerical simulations and experiments, we demonstrate that comparing with true autocorrelation, the pattern of R-autocorrelation has a significantly lower background and higher contrast, which enables better reconstructions of hidden objects, especially in the case of broadband illumination, or even with white-light

Tunable Plasmon Resonances and Enhanced Local Fields of Spherical Nanocrescents

The tunable plasmon resonances of nanostructures with sharp features play an important role in the surface-enhanced spectroscopy. The maximum enhancement factor can be achieved by tuning the resonance wavelengths. In this study, the discrete-dipole approximation was used to investigate the resonance modes of the spherical nanocrescents that possess the hot spots located at the ring-tip. We applied the plasmon hybridization theory to interpret the excitation and shift of resonance modes of the nanostructure with reduced symmetry. The resonance wavelengths can be tuned from the visible to the near-infrared regime by varying the geometrical parameters. The intraparticle coupling at the ring-tip explained the significant influence of the incident light polarization on the enhancement of local fields. The spherical nanocrescents can be developed as a powerful substrate in surface-enhanced spectroscopy for the tunable plasmon resonances and enhanced local fields

Supplementary document for Multiplexed wavefront sensing with a thin diffuser - 6774961.pdf

Revised supplemental informatio

Data.rar

Dataset for validating multiplexed wavefront sensing with a thin diffuser

Supplementary document for Multiplexed wavefront sensing with a thin diffuser - 6856404.pdf

Supplemental documen

Mixed-integer programming model and hybrid local search genetic algorithm for human–robot collaborative disassembly line balancing problem

Human–robot collaborative technology maximises the advantages of the capabilities of humans and robots, and provides diverse operating scenarios for the remanufacturing industry. Accordingly, this paper proposes an innovative human–robot collaborative disassembly line balancing problem (HRC-DLBP). First, a mixed-integer programming (MIP) model is devised for the HRC-DLBP to minimise the number of workstations, smoothness index, and various costs. Second, a hybrid local search genetic algorithm (HLSGA) is developed to solve the proposed HRC-DLBP efficiently. According to the problem characteristics, a four-layer encoding and decoding strategy was constructed. The search mechanism of the local search operator was improved, and its search strategy was adjusted to suit the genetic algorithm structure better. Furthermore, the accuracy of the proposed MIP model and HLSGA is verified through two HRC-DLBP examples. Subsequently, three HRC-DLBP examples are used to prove that the HLSGA is superior to five other excellent algorithms. The case of the two-sided disassembly line problem reported in the literature is also solved using the HLSGA. The results are found to be significantly better than the reported outputs of the improved whale optimisation algorithm. Besides, HLSGA also outperforms the results reported in the literature in solving EOL state-oriented DLBP. Finally, the HLSGA is applied to a power battery disassembly problem, and several optimal allocation schemes are obtained.</p

Codes_v2.rar

This supplementary Material includes: •The raw data corresponding to the multiplexed speckle maps for the two experiments shown in Figure 2 (3 multiplexed wavefronts) and Figure 3 (5 multiplexed wavefronts) of the article. •The Matlab codes used to reconstruct the various multiplexed wavefronts from these speck-le maps (MAIN1_Multiplex.m) which is the heart of this article. This code will allow readers to check the impact of each reconstruction parameter (e.g. number of iterations, macropix-el size…) •The raw data corresponding to each wavefront, acquired individually using a standard non-multiplexed method . •A Matlab code (MAIN2_Comparison.m) allowing a quantitative comparison of the wave-fronts reconstructed using our multiplexing method to wavefronts acquired individually. •A Matlab code (MAIN3_Multiplex_AO.m) is an modification of (MAIN1_Multiplex.m), in which the direct DIC (T=1) is used with big phase-pixel to reconstruct the wavefront. Parfor loop is used for processing each GS running in a parallelization mode

Single-shot Digital Optical Fluorescence Phase Conjugation Through Forward Multiply Scattering Samples

Aberrations and multiple scattering in biological tissues critically distort light beams into highly complex speckle patterns. In this regard, digital optical phase conjugation (DOPC) is a promising technique enabling in-depth focusing. However, DOPC becomes challenging when using fluorescent guide-stars for four main reasons: The low photon budget available, the large spectral bandwidth of the fluorescent signal, the Stokes shift between the emission and the excitation wavelength, and the absence of reference beam preventing holographic measurement. Here, we demonstrate the possibility to focus a laser beam through multiple-scattering samples by measuring speckle fields in a single acquisition step with a reference-free and high-resolution wavefront sensor. By taking advantage of the large spectral bandwidth of forward multiply scattering samples, Digital Fluorescence Phase Conjugation (DFPC) is achieved to focus a laser beam at the excitation wavelength while measuring the broadband speckle field arising from a micron-sized fluorescent bead