For conventional ghost imaging (GI) systems, the object image is obtained based on the reflective or transmissive character of the object. When the object and its background have the same reflectivity or transmittance, conventional GI is helpless in detecting the object from the background. An improvement is to use the polarization components of the reflected or transmitted light. We propose a polarimetric GI system that employs a polarization state generator and a polarization state analyzer. This feature allows for the first time, to the best of our knowledge, imaging the object buried in the same reflectivity or transmittance background, which represents a breakthrough for GI applications. Using a combination of intensity and polarization information, we are better able to distinguish between the background and the different material objects.
Single-pixel imaging has the ability to generate images at nonvisible wavelengths and under low light conditions and thus has received increasing attention in recent years. Fourier single-pixel imaging (FSI) utilizes deterministic basis patterns for illumination to greatly improve the quality of image reconstruction. However, the original FSI based on grayscale Fourier basis illumination patterns is limited by the imaging speed as the digital micro-mirror devices (DMD) used to generate grayscale patterns operate at a low refresh rate. In this paper, a new approach is proposed to increase the imaging speed of DMD-based FSI without reducing the imaging spatial resolution. In this strategy, the grayscale Fourier basis patterns are split into a pair of grayscale patterns based on positive/negative pixel values, which are then decomposed into a cluster of binary basis patterns based on the principle of decimalization to binary. These binary patterns are used to illuminate the imaged object. The resulting detected light intensities multiply the corresponding weighted decomposed coefficients and are summed, and the results can be used to generate the Fourier spectrum for the imaged object. Finally, an inverse Fourier transform is applied to the Fourier spectrum to obtain the object image. The proposed technique is verified by a computational simulation and laboratory experiments. Both static and dynamic imaging experiments are carried out to demonstrate the proposed strategy. 128 × 128 pixels dynamic scenes at a speed of ~9 frames-per-second are captured under 22 KHz projection rate using a DMD. The reported technique accelerates the imaging speed for DMD-based FSI and provides an alternative approach to improve FSI efficiency.
In theory, lidar overlap factor can be derived from the difference between the particle backscatter coefficient retrieved from lidar elastic signal without overlap correction and the actual particle backscatter coefficient, which can be obtained by other measured techniques. The side-scatter signal using a CCD camera is testified to be a powerful tool to detect the particle backscatter coefficient in near ground layer during night time. In experiment, by combining side-scatter and back-scatter signals the geometric form factor for vertically-pointing Mie lidar in 532 nm channel is determined successfully, which is corrected by an iteration algorithm combining the retrieved particle backscatter coefficient using CCD side-scatter method and Fernald method. In this study, the method will be expanded to 1064 nm channel in dual-wavelength Mie lidar during routine campaigns. The experimental results in different atmosphere conditions demonstrated that the method present in this study is available in practice.
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