To suppress tilt-to-length (TTL) coupling induced by the relative jitter between the optical bench and the telescope, a coaxial entrance-exit pupil configuration is required. Compared to existing non-coaxial schemes, this configuration enables direct beam exchange without auxiliary folding mirrors on the optical bench, thereby inherently eliminating a primary noise path induced by relative opto-mechanical motion. In an off-axis four-mirror telescope, achieving pupil co-alignment demands large tilts on tertiary (M3) and quaternary (M4) mirrors, which rapidly increase aberrations. We employ third-order vector aberration theory as an effective tool for screening initial configurations to establish the quantitative relationship between mirror tilt angle and wavefront root-mean-square (RMS), enabling the selection of a favorable initial configuration. Furthermore, circular-domain Zernike polynomials are analytically expanded under an elliptical pupil, providing initial coefficients for freeform optimization. Using these analytic initial values, a coaxial-pupil afocal telescope is designed, achieving a wavefront RMS≤0.004λ at 1064nm and an intrinsic TTL≤0.004pm/nrad, both within the science field of view.

In this paper, a dual-layer metamaterial structure operating in the microwave band which is composed of nested split-ring resonators (SRRs) was designed. The electromagnetic transmission under two polarization modes are comparatively analyzed through the finite integral time domain method. By scrutinizing the electric field distribution on each resonance frequency, the physical mechanism of the electromagnetically induced transparency (EIT)-like effect is expounded, and the influence of the structure parameters was further investigated. The experimental results obtained from the microwave anechoic chamber closely match with the simulation results. The experimental findings suggest that the metamaterial structure has potential applications in the detection of solid material permittivity.

In this paper, a novel fiber-optic wearable sensor, to our knowledge, is proposed and completed experimentally based on core-mismatched multimode fibers with core-offset splicing. The spectral characteristics are simulated and analyzed with varied offset and lengths, and the comprehensive tests in terms of curvature and temperature responses are performed under the optimal offset. The experimental results show that the wavelength responses of curvature are directly related to the length of the offset-multimode-fiber, and the maximum reaches -25.41nm/m-1 with a temperature sensitivity of 50.47pm/°C. Furthermore, the intensity-demodulated-based real-time monitoring setup is built, and the encapsulated sensor is applied to rapid joint movement scenarios of the knee, elbow, and finger, respectively. The tested results show that a large bending angle (close to 90°) can be achieved with a real-time response (∼0.2s) and a high signal-to-noise ratio.

Most snapshot color imaging devices adopt a single sensor with a Bayer color filter array (CFA), where only one RGB component is captured at each pixel, requiring demosaicking to recover full-color images. Existing methods range from fast interpolation to deep learning approaches with high reconstruction accuracy but often suffer from a trade-off between performance and computational complexity. To address this issue, we propose an efficient demosaicking method based on dynamic weight learning. The proposed network adaptively computes layer-wise feature weights without increasing model parameters and incorporates a mixed-attention block to jointly exploit global and local information, effectively reducing reconstruction artifacts. Extensive experiments demonstrate superior performance over that of existing methods.

Single-pixel imaging (SPI) is a computational imaging architecture that utilizes non-resolution detectors to acquire two-dimensional and three-dimensional image information under structured illumination. This method possesses strong anti-interference capability under low-light conditions and has great potential for applications. However, the imaging quality and reconstruction efficiency of SPI remain significant constraints on its practical applications under low sampling conditions. Here, we propose a non-pre-trained complex-valued network-based compressive Fourier SPI technique to obtain a high-performance reconstructed image at a low sampling rate. This technique utilizes a physical model as prior information to achieve network-driven optimization and thus does not need to be pre-trained on any dataset. The performance is demonstrated simultaneously by simulation analysis and experimental validation, showing a peak signal-to-noise ratio of 23.68dB at a sampling rate of 0.05 for 64×64pixel images. The proposed complex domain network-based compressive SPI imaging scheme paves the way for practical applications.

Reliable manufacturing and high optical performance of plano-convex aspheric lenses necessitate an improved optical design characterized by an optimal refractive index of the lens material and the prevention of the slope surface shape oscillations, which provide an increased angular field of view and low sensitivity to misalignments. To formulate the criteria for the optimal refractive index, we propose an analytical representation of the optimal aspheric surface based on the Fermat's principle in the form of parametric functions of coordinates, allowing the surface to be approximated by the elliptical conic section expanded with high-order aspheric deformation terms starting from the 6th power. There are determined the ranges of optimal refractive indices for materials of plano-convex aspheric lenses: n=1.605…1.665 for an aplanatic design with the Abbe sine condition fulfilled, ensuring low lens sensitivity of the lens to angular misalignment; n=1.735…1.835 for sharp imaging of elongated longitudinal objects in accordance with the Herschel's condition.

Existing indoor positioning methods in visible light communication systems typically rely on large databases, powerful signal processing units, and additional sensors such as gyroscopes, which limit their applicability in efficiency-sensitive scenarios. To address this issue and achieve an optimal balance between positioning accuracy, inference time, and model size, we propose uniform and power-of-two quantization on a multi-head ResNet50 (UPU-MH-ResNet50) algorithm in this paper. The proposed algorithm does not require additional sensors and can accurately estimate the three-dimensional coordinates of the receiver, including X and Y coordinates and rotation angle. It effectively mitigates the impact of random angle changes on positioning accuracy, significantly enhancing the system's robustness. Additionally, the algorithm is further optimized through model quantization to reduce computational costs. We conducted validation on a self-built experimental testbed in a laboratory environment with dimensions of 2.6m×2.6m×2.2m and a receiver rotation angle range of ±30∘. Within this tilt range, 90% of the 3D positioning errors are controlled within 2cm. Moreover, the proposed 4-bit UPU-MH-ResNet50 achieves a 7.7× reduction in model size and a 2.7× speedup in inference, where the acceleration and efficiency results are measured from the GPU-based implementation using real captured data collected on the developed testbed, indicating high energy efficiency.

Terahertz metasurface lenses are widely used due to their high design flexibility and ultra-thin characteristics, but they have an inherent bottleneck of a significant decrease in efficiency when turning large-angle beams. Therefore, this paper proposes a metagrating, aiming to develop terahertz devices with wideband response, large-angle control, and efficient beam deflection. The results demonstrate that when the deflection angle is 71.3°, the efficiency exceeds 70%. In addition, within a relative bandwidth of 15%, the metagrating maintains a diffraction efficiency exceeding 50%, and the beam deflection range is 56.79° to 84.88°. This research has confirmed the outstanding potential of metagrating to achieve high efficiency, broadband, and large-angle beam deflection.