- 标题
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A blue-phase liquid crystal lens array based on dual square ring-patterned electrodes
摘要： We propose a blue-phase liquid crystal (BPLC) lens array based on dual square ring-patterned electrodes. A high dielectric constant layer is used to smoothen out the horizontal electric field and reduce the operating voltage. By creating a potential difference between the dual square ring-patterned electrodes, gradient electric fields are generated and lens-like phase profile is obtained. Besides, the focal length of the BPLC lens is adjustable with voltage changes and all simulation results indicate that the BPLC lens array is polarisation-insensitive.
关键词： polarisation-insensitive,lens array,Blue phase,liquid crystal
更新于2025-09-23 15:21:01
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Experimental demonstration of imaging hidden objects in opaque liquid-based media by fusion of single-shot multiview polarized and unpolarized speckle images
摘要： Turbid water-based liquids are common scattering media within which imaging objects is challenging, since scattering particles of various origins and sizes may cause severe image degradation, resulting in poor object recovery and resolution. Therefore, counteracting the nontrivial effects of light scattering is a primary challenge, limiting the utility of optical imaging within liquid media. In this work, we sought to circumvent the optical degradation in turbid liquid media and to recover high-quality images of hidden objects by averaging polarized speckle images projected from several directions through a lens array. Inspired by astronomy imaging techniques, the averaging process utilized a Shift-and-Add (SAA) algorithm developed to reconstruct atmospherically-degraded solar images. Both linear and circular polarization strategies were then applied to further improve image reconstruction. Experiments were carried out using two targets, each having a distinct geometrical shape, embedded within turbid liquid media comprising a range of dilutions of commercially available cow’s milk in seawater. The media were irradiated with a polarized laser beam, after which multiple polarized speckled images were captured with a CCD camera. Offline, images were first shifted to a common center and then fused, using the SAA algorithm, to yield reconstructed images of each hidden object. Quantitative image quality metrics, including SNR, entropy, and sharpness were applied to evaluate quality of the reconstructed images. The reconstructed images obtained demonstrate successful adaptation of our methodology for the identification of hidden objects within turbid media. To the best of our knowledge, this is the first report to demonstrate successful imaging of hidden object images within turbid liquid media by averaging multiple polarized speckle projections.
关键词： Linear and circular polarization,Imaging through turbid water,Lens array,Multiple polarized speckle projections,Image processing
更新于2025-09-19 17:15:36
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[IEEE 2018 8th International Conference on Localization and GNSS (ICL-GNSS) - Guimaraes (2018.6.26-2018.6.28)] 2018 8th International Conference on Localization and GNSS (ICL-GNSS) - Direct position estimation from wavefront curvature with single antenna array
摘要： In this paper we investigate the possibility to perform direct positioning by retrieving information from the wavefront curvature. Despite such an approach has been considered in the past at microwave and acoustic frequencies using extremely large antennas, it is of interest to investigate its potential exploitation at mm-wave with practical size antennas in the context of next 5G systems. Thus, here we first consider a dedicated model to gather the source position information from the wavefront curvature for different array architectures, i.e., traditional and lens-based arrays, and successively we derive the maximum likelihood estimator to investigate the attainable performance. Results, obtained for different number of antennas, i.e., for different array apertures, confirm the possibility to achieve interesting positioning performance using a single antenna array with limited dimensions.
关键词： mm-wave,direct positioning,massive array,lens array,Wavefront curvature
更新于2025-09-11 14:15:04
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A two-step calibration method of lenslet-based light field cameras
摘要： The calibration of lenslet-based light field camera is the key issue to many applications, especially the three-dimensional shape measurement. In this paper, a two-step physically based calibration method is proposed, where every parameter is described with its own physical meaning. The parameters about the main lens of the light field camera are calibrated with the central sub-aperture image, and the parameters about the micro-lens array are calibrated with the epipolar images, subsequently. To improve the calibration result, the distortion correction of the main lens and a nonlinear optimization method are applied also. The calibration method is validated with a commercially available light field camera and compared to Dansereau’s calibration method. Typical RMS reprojection errors are 0.0017, 0.0032 mm for 30.0, 35.1 mm calibration grids.
关键词： Micro-lens array,Light field camera,Light field,Calibration,Main lens
更新于2025-09-04 15:30:14