Hyperspectral image super-resolution has been extensively studied, and significant development has been made based on deep convolutional neural networks (CNNs). Particularly, residual networks that fuse features from multiple layers have achieved high-accuracy hyperspectral image super-resolution. However, most residual networks tend to straightforwardly add features from one layer to another through skip-connections that may cause confusion about feature fusion. To tackle this issue, we develop a ConvLSTM skip-connection strategy that characterizes features from consecutive layers by ConvLSTMs and renders feature fusion in a more principal manner. Accordingly, we develop a super-resolution framework that consists of three modules. The first module, i.e., spatial feature reconstruction, employs the ConvLSTM skip-connections to comprehensively fuse spatial features from different layers. The second module, i.e., edge refinement, involves the ConvLSTM skip-connections to enhance the edge information from intermediate results. The third module, i.e., spectral information reconstruction, refines spectral features by capturing interactions between different spectral bands through the ConvLSTM skip-connections. The three complementary modules cooperate such that both spatial resolution and spectral fidelity are well maintained. Extensive experimental results on the Chikusei, Houston, and QUST-1 datasets demonstrate that our framework outperforms state-of-the-art methods in terms of quantitative evaluation and visual quality across a variety of scenarios. We release our source code at https://gitee.com/xu_yinghao/CLSCNet for public evaluations.

Freeform surfaces have the advantage of balancing off-axis aberration. In this paper, based on the framework of nodal aberration theory (NAT) applied to the coaxial system, the third-order astigmatism and coma wave aberration expressions of an off-axis system with Zernike polynomial surfaces are derived. The relationship between the off-axis and surface shape acting on the nodal distributions is revealed. The nodal aberration properties of the off-axis freeform system are analyzed and validated by using full-field displays (FFDs). It has been demonstrated that adding Zernike terms, up to nine, to the off-axis system modifies the nodal locations, but the field dependence of the third-order aberration does not change. On this basis, an off-axis two-mirror freeform system with 500 mm effective focal length (EFL) and 300 mm entrance pupil diameter (EPD) working in long-wave infrared is designed. The field constant aberrations induced by surface tilting are corrected by selecting specific Zernike terms. The design results show that the nodes of third-order astigmatism and coma move back into the field of view (FOV). The modulation transfer function (MTF) curves are above 0.4 at 20 line pairs per millimeter (lp/mm) which meets the infrared reconnaissance requirement. This work provides essential insight and guidance for aberration correction in off-axis freeform system design.

The division of focal plane (DoFP) polarization imaging sensors, which can simultaneously acquire the target’s two-dimensional spatial information and polarization information, improves the detection resolution and recognition capability by capturing the difference in polarization characteristics between the target and the background. In this paper, we propose a novel polarization imaging method based on deep compressed sensing (DCS) by adding digital micromirror devices (DMD) to an optical system and simulating the polarization transmission model of the optical system to reconstruct high-resolution images under low sampling rate conditions. By building a simulated dataset, training a polarization super-resolution imaging network, and showing excellent reconstructions on real shooting scenes, compared to current algorithms, our model has a higher peak signal-to-noise ratio (PSNR), which validates the feasibility of our approach.

This paper presents a study on a quadrotor unmanned aerial vehicle (UAV) fault-tolerant control scheme. According to the attitude model and safety control of the aircraft under the uncertainty of inertial matrix, the attitude state constraint by reinforcement learning is designed to ensure safety. Even if the boundary is crossed, it can be pulled back to the boundary by means of a designed penalty function with reinforcement learning. Meanwhile, in order to inhibit the oscillation caused by immediate reward as usual, an adaptive update law is proposed. Furthermore, considering the coupled actuator fault and system input saturation due to uncertainty of inertial matrix, the Nussbaum-type function is utilized in this work to handle this challenge, which likely causes the singularity of inertia matrix. As a consequence, combined with the Lyapunov stability theory, it is confirmed that the proposed FTC scheme ensures that all the closed-loop signals are bounded. Simulation results are carried out to illustrate the effectiveness and advantage of the proposed control scheme.

Owing to the wide application of freeform surfaces in off-axis optical systems with large apertures, large fields of view, and long focus distances, the polarization effects caused by non-rotationally symmetrical surfaces have a significant impact on the system’s polarization imaging quality and measurement accuracy. In this study, considering the problem of the aforementioned polarization effects, a polarization aberration analysis method based on the Jones notation using the fringe Zernike polynomials freeform surface is proposed. A full-field polarization aberration analysis model of a non-rotationally symmetric reflection optical system with a freeform surface is constructed. The effect of freeform surfaces on the distribution characteristics of the proposed model is demonstrated. Through the full-field polarization ray tracing of the field-of-view off-axis optical system, three kinds of polarization aberrations, comprising phase aberration, retardance, and diattenuation are obtained, after the introduction of the Zernike polynomial freeform surface. Finally, a full-field polarization aberration analysis is carried out for a wide-field off-axis three-reflection optical system with freeform surfaces. The results show that the phase aberration of a non-rotationally symmetric optical system with freeform surfaces is directly related to the freeform surface shape. The full-field of view distribution of the retardance and diattenuation caused by the free-form surface is 52.5% of the overall retardance and diattenuation distribution of the system. The proposed method will be of great significance for improving the accuracy of systems in deep-space telescopes and lithography objectives.

In the field of compressed imaging, many attempts have been made to use the high-resolution digital micromirror array (DMD) in combination with low-resolution detectors to construct imaging systems by collecting low-resolution compressed data to reconstruct high-resolution images. However, the difficulty of achieving micrometer-level alignment between DMD devices and detectors has resulted in significant reconstruction errors. To address this issue, we proposed a joint input generative adversarial network with an error correction function that simulates the degradation of image quality due to alignment errors, designed an optical imaging system, and incorporated prior imaging system knowledge in the data generation process to improve the training efficiency and reconstruction performance. Our network achieved the ability to reconstruct 4× high-resolution images with different alignment errors and performed outstanding reconstruction in real-world scenes. Compared to existing algorithms, our method had a higher peak signal-to-noise ratio (PSNR) and better visualization results, which demonstrates the feasibility of our approach.