Optical Review最新文献

Monitoring the polarization signature of the sky is valuable for navigation, meteorology, and remote sensing. However, the neutral points—Babinet (above the Sun), Brewster (below the Sun), Arago (above the anti-Sun), and the Fourth (below the anti-Sun)—remain underutilized as meteorological tools. The neutral points are formed through multiple scattering, making them useful markers for atmospheric turbidity, but further research is needed to understand their positional changes under varying conditions. This study presents the development of the Ultraviolet Linear Stokes Imaging Polarimeter (ULTRASIP), which operates at a center wavelength of 355 nm with a 10 nm bandpass and an instantaneous field of view of 7.2 arcseconds/pixel. A novel estimation technique to determine the position of the neutral point from linear Stokes images is applied to 10 h of observations. The true position of the neutral point is unknown, so the Babinet neutral point positions are reported with linear regression uncertainties. The position of the Babinet neutral point was found with azimuth uncertainties ranging from 2.52 to 21.96 arcseconds and altitude uncertainties ranging from 2.16 to 5.40 arcseconds. To the authors’ knowledge, these are the first images of the Babinet neutral point in an ultraviolet waveband. The development of ULTRASIP and neutral point position estimation technique will support future correlation studies between neutral point positions and atmospheric turbidity.

Given the challenges faced by object detection methods that rely on visible light in complex environments, many researchers have begun to explore the combination of infrared and visible imaging for multi-modal detection. Existing results show that multi-modal fusion has proven effective for improving object detection outcomes. However, most current multi-modal detection methods rely on fixed-parameter feature fusion techniques, failing to account for the imaging differences across diverse environments and the complementary information between different modalities. In this paper, we propose a multi-modal object detection method based on adaptive weight fusion, utilizing the dual-stream framework to extract features from both modalities separately. We design a Cross-Modal Feature Interaction (CMFI) module to integrate global information across modalities and capture long-range dependencies. In addition, we introduce an Adaptive Modal Weight Calculation (AMWC) module, which fully accounts for the characteristics of different modalities in various environments and the complementarity among the modalities. This module dynamically adjusts the fusion weights within the CMFI module based on the input from different modalities. Moreover, a novel loss function is introduced to regulate the internal parameter adjustments of the AMWC module. We conduct extensive experiments on three representative datasets, using mAP@0.5 and mAP@0.5:0.95 as evaluation metrics. Our model achieved 79.1% and 40.6% on the FLIR dataset, 81.9% and 52.1% on M3FD, and 73.5% and 32.5% on KAIST.

In this paper, we investigate and analyze the optical unidirectional transmission based on a tapered fiber-based asymmetric Sagnac interferometer. By carefully designing the asymmetric structure, there are the different coupling conditions and different intensities of multi-mode interferences in the Sagnac loop when the light enters from the different input ports. The maximal difference of the transmission spectra between the forward propagation and the backward propagation is up to 40.4 dB. Furthermore, by using as an extensible topological structure, two fiber Sagnac loops are arranged to realize the three-port circular propagation, showing the strict transmitting order in the three ports, along with the blocked propagation in the reverse order. Meanwhile, three fiber Sagnac elements are also arranged to achieve the four-port circular propagation, also along with the strict pass order. With ultra-compact size, wideband, and great extensibility, this proposed fiber device is competitive to be the attractive building blocks for the integrated photonic circuits.

Spherical markers are important in near-infrared (NIR) locators of orthopedic surgical robots. The spherical markers suffer from poor occlusion resistance due to occlusion by medical staff or blood contamination. Solutions to this challenge, such as adding markers or cameras, are limited by space and system complexity in the surgical environment. Compared with spherical markers, planar markers have better potential to enhance occlusion resistance due to their rich feature points. Current planar markers, which are designed for visible light locators in augmented reality (AR) applications, do not fulfill the dual requirements of occlusion resistance and miniaturization necessary for orthopedic surgical robots. Therefore, this paper will concentrate on the anti-occlusion of NIR small-size planar markers. The designed planar marker employs a checkerboard layout embedded in circular patterns to achieve orientation encoding, ID encoding, and redundant encoding mechanisms at the same time. A projective transformation with minimal representations of uncertain image points enhanced planar markers’ pose estimation. In translation and rotation experiments, the marker presented better results compared with two other planar marker systems: the classical ArUco and the advanced TopoTag. Moreover, the designed planar marker with redundant encoding can maintain pose estimation even with occlusion levels reaching up to 50%. Therefore, this paper offers a promising solution for enhancing the occlusion resistance of NIR planar markers.

The holographic Maxwellian display, as a promising technique, offers a potential solution to the vergence–accommodation conflict in see-through near-eye displays for augmented reality applications. However, traditional holographic Maxwellian displays primarily rely on iterative or non-iterative algorithms, which face the challenge of balancing image quality and computational efficiency. To address this issue, we propose a lensless phase-only holographic Maxwellian display based on a complex-valued convolutional neural network algorithm. The complex-valued convolutional approach captures both the phase and amplitude information of light waves, enriching the holographic details and significantly improving the quality of the reconstructed images. Simulation results demonstrate that the quality of the reconstructed image can be significantly enhanced while maintaining high computational efficiency compared to conventional algorithms. Furthermore, by multiplying the phase hologram with a convergent spherical wave at the hologram plane, the virtual target image is focused on the viewer's pupil, ensuring a consistent perception of all-in-focus images at the pupil's location. To expand the size of the eyebox, multiple digital spherical waves were employed in the holographic Maxwellian display. Finally, experimental results validate that our proposed near-eye display system successfully generates see-through virtual images, effectively eliminating the vergence–accommodation conflict. The demonstrated capabilities of the proposed method underscore its considerable potential for applications in holographic near-eye displays.

This project presents the design and fabrication of a polarization-independent liquid crystal-on-a-silicon (PI-LCoS) phase modulator that utilizes a polymer quarter-wave plate (QWP) for polarization conversion. The device features a novel silicon backplane including DRAM-based analog pixel circuit with fine grayscale control, and small pixel size, achievable using standard foundry processes. We demonstrate polarization-independent phase modulation through beam steering tests under various input polarizations, achieving high optical efficiency and low polarization-dependent loss (PDL) of less than 0.6 dB. The proposed device, with its frame-at-a-time update and simplified waveplate fabrication process, offers significant advantages for commercial applications such as wavelength-selective switches, holographic displays, adaptive optics, and free-space optical communication systems.

This paper presents a new method for analyzing ghost paths for camera lens design using a method that predefines ray orders and uses cloud-based parallel processing. Our method enables comprehensive ghost analysis of complex optical systems with multiple reflections, which were previously considered computationally impractical. The performance evaluation demonstrated the successful processing of over 4.4 billion rays through complex optical paths, completing calculations within practical time constraints.

To enhance chaotic complexity and conceal time-delay signatures, we propose an optically chaotic secure communication system. The system combines chaotic intensity signals from an amplified spontaneous emission (ASE) noise source with an electro-optical phase delay oscillating feedback loop through optical injection. It integrates all-optical intensity chaos and electro-optical feedback to produce complex chaotic signals. ASE noise acts as an entropy source, while a fiber Bragg grating (FBG) enhances signal complexity by leveraging its dispersion properties. This approach significantly expands the system’s key space. The transmitted information is nonlinearly coupled with the chaotic carrier via phase modulation, contributing to the chaotic carrier’s generation. At the receiver, optical chaotic synchronization decrypts the transmitted signals. Performance analysis shows that the system effectively hides time-delay signatures, increases chaotic complexity, and exhibits strong resistance to parameter mismatches. These results demonstrate its high security for physical-layer communication.

This study proposes a solid-state device that can be updated to high-response spatial light modulators. We demonstrate an electro-optic grating device based on the Kerr effect in potassium tantalate niobate (KTN) crystals that exhibit a relative dielectric constant exceeding 10,000. The time response in spatial light modulation can be enhanced by a quadratic electro-optic material with high permittivity. Its effectiveness may be affected by device specifications such as spatial resolution, temporal stability, and electrode-matching conditions on a specific surface. We conducted simulations using the finite element method to verify their effects, calculating the electric potential while applying voltage to the crystal. The field of light inside the crystal was computed sequentially according to the wave propagation equation and the potential. Fourier analysis of the light modulated in the simulations indicated that the spatial crosstalk in the grating pattern can primarily be attributed to the internal charge gradient. In the experiments, a transparent comb electrode was deposited on both sides of the KTN crystal to generate phase patterns of the grating in response to the voltage. After switching on the voltage using the function generator, the delay in the detection of light diffraction through the device and lens was measured. The frequency dependence of the measured capacitance was determined to be stable up to the cutoff frequency.

A bundle of digitally directed beams, capable of instantaneously controlling their direction at every point within a field of view, is proposed for the inspection of microscale defects in manufacturing processes.