Two-dimensional phase unwrapping is a key step for interferometric synthetic aperture radar to obtain elevation, and it is also an indispensable step in the process of elevation inversion. However, under the condition of strong noise, traditional unwrapping methods cannot achieve high quality phase recovery. To solve the problem, we used a neural network to unwrap the phase. The proposed method is validated compared with several conventional methods, and the experimental results show that the neural network method can obtain better effect under the condition of strong noise.
Due to the absorption and scattering effect of the atmosphere, it is difficult to extract effective target information from the image sensor under severe hazy conditions. We propose an end-to-end convolutional neural network designed to solve the problem of image restoration in scattering imaging. And we explicitly consider the atmospheric scattering model of the hazing process in the network design. The encoder and decoder modules are used for feature extraction, and the pyramid pooling network is used to preserve the multi-scale features of the image. The attention mechanism is introduced in the network. Encoder module is adopted for BoTNet that incorporates self-attention for multiple computer vision tasks. Due to the lack of real hazy images, we collected scattered images under low visibility conditions and corresponding haze-free images. We examine the proposed method by the challenge datasets, the experiments demonstrate that the proposed method can effectively extract and recover the feature information of the target. The results show that, compared with the traditional signal processing method, our model achieves significant practical performance gains and restores the detailed information of the image.
In Computational Spectral imaging, two-dimensional coded apertures and dispersive elements realize the mixed modulation of spatial information and spectral information of the target respectively, and then reconstruct the threedimensional data cube. Therefore, coded aperture plays a vital role. In the imaging process, by moving the coded aperture to increase the number of measurements, the aperture moved one code element at each step to simulate the actual push-broom process. Three types of coded apertures were considered, which are Gauss random coded aperture, Hadamard coded aperture and Harmonic coded aperture, and the reconstruction effect of the three coded apertures were analyzed. The Least Square (LS) algorithm was considered to reconstruct three-dimensional data cube. Compared with the classical Two-step Iterative Shrinkage/Thresholding (TwIST) algorithm, the reconstructed Structural Similarity Index Measurement (SSIM) and Peak Signal to Noise Ratio (PSNR) by LS algorithm were better than TwIST algorithm. It was indicated that the SSIM and PSNR increased with the increasing number of measurements. When the number of measurements was similar with the number of spectral segments, the SSIM of the three coded apertures reached more than 0.9 by LS algorithm. However, the SSIM and PSNR of the Gauss random coded aperture were the largest Obviously, which are 0.995 and 52.560, respectively. And the PSNR of Gauss random coded aperture was 13 dB more than that of Hadamard and Harmonic coded apertures. When the number of measurements was constant, the SSIM and PSNR decrease gradually with the increasing number of spectral segments. The simulation results showed that the LS algorithm was superior to the TwIST algorithm in the reconstruction process, and the Gauss random coded aperture had the best performance.
Super-resolution hyperspectral imaging is a key technology for many applications, especially in the fields of remote sensing, military, agriculture, and geological exploration. Recovering a high resolution image needs enormous data, which puts forward very high requirements on image system hardware. Compressed sampling spectral imaging technology could well solve this problem and achieve high-resolution objects with low-resolution compressed data. In this paper, the method of a compressed sampling spectral imaging based on push-broom coded aperture and dispersion prism is proposed. A spectral aliasing image is formed when the object passing through the dispersive prism. According to the prism dispersion condition and the CCD pixel size, the visible spectrum can be divided into N spectral bands, and the measurement matrix of the coded aperture is respectively calibrated for the center wavelength of each spectral band. By controlling a stepper to implement the push broom of the coded aperture to change the measurement matrix, multiple spectral aliasing images can be obtained. The pixel size of the coded aperture becomes half of the CCD by a relay lens, which means the pixel of CCD is low-resolution for the coded aperture. The super-resolution hyperspectral image of the object is obtained by the improved LS reconstruction algorithm. Simulation results show that, the recovered hyperspectral image has twice resolution compared with the low-resolution CCD image, and the peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) increase with the increasing compressed sampling hyperspectral images. For N=31, the average PSNR and SSIM recovered from six aliasing images is 22.019 and 0.235, respectively. The average PSNR and SSIM of the recovered 31 bands are also increasing with increasing aliasing images. While the aliasing imaging is 156, The average PSNR and SSIM exceeds 38 and 0.9. This method proves that super-resolution hyperspectral imaging can be achieved by capturing less low-resolution object images.
In this paper, a technology of multi-radar imaging based on compressed sensing is proposed to improve image resolution. By constructing sample matrix, multi-radar super-resolution imaging is transformed to a compressed sensing problem. Utilizing the signal’s sparsity, super-resolution image can be obtained by solving an optimization problem. Simulation shows effectiveness of this technology.
Compressive imaging(CI)can offer a versatile improvements for imaging systems, such as smaller compressed data volume and super-resolution. Among various methods to realize Compressive imaging, pushing encoding mask has attracted the most attention with its compatibility to the space remote sensing. However, complex pre- calibrations are usually needed for calibrating the encoding mask to achieve the measurement matrix for the image reconstruction. Herein, we design a pushing compressive imaging system which fixed with the function of situ calibration of the encoding mask. The pushing compressive imaging system was constructed, and the experimental results confirmed that the system had the ability for data compression and super-resolution. And above all, the system can avoid the complex pre-calibration, which makes the on-orbit calibration feasible. In the simulations, twice, three times and four times resolutions higher than the captured image’s resolution are performed respectively, which confirm that the method can improve the target image resolution based on the relative low resolution raw captured target images. Furthermore, by pushing the mask precisely which can be considered equivalent to the real pushing imaging, we have reconstructed the true super-resolution target image accurately based on the mask calibration and 6 captured pushing imaging frames.
An adaptive total variation method to reduce speckles with preservation of targets in synthetic aperture radar (SAR) images is investigated. Based on the gamma distribution of speckle, an adaptive total variational model is proposed with its fidelity term derived from a framework of weighted maximum likelihood estimation and its regularity term with constraints on the gradient of an image. It has merits of preserving textures and targets since the a priori distribution of noise is incorporated into the model and the weights are essentially image data driven, which can adaptively adjust the weights. The mathematical analysis is carried out, and proof of existence and uniqueness of a solution for the corresponding function is also presented. Theoretical analysis and experiments on both the simulated and real SAR images demonstrate that the method proposed here performs favorably.
We describe an optical imaging system based on random phase modulation and sparse sampling. The system is also an application of compressive sensing in the field of imaging. Different from the Rice compressing imaging system, the imaging system needs only a signal exposure. Meanwhile, the space-bandwidth product of the system is extended, which means the pixels of imaging sensor can be reduced without a loss of image's resolution. A random phase modulation is employed to make the energy of optical field spread out across the entire modulated image, which can facilitate the sampling process. A random sparse sampling scheme is designed to effectively reduce the pixels of imaging sensor, and the sensing matrix is uncorrelated with arbitrary sparse representation matrix. The feasibility of the proposed system is validated by numerical experiments.
An exact and closed-form algorithm for InSAR geolocation is studied, then on the basis, an analysis of error propagation between measurements and geolocation solution was given. At the same time, from a new point of view, we propose a new method focused on the compensation of the difference of the slant ranges of two satellites. Eventually, appalling a method of baseline estimation which based on GCPs, we can obtain high precision baseline estimation from geolocation solutions after error compensation.
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