To achieve the integrated detection of large-aperture segmented optical systems and avoid the manufacture of equal-aperture detection devices, we propose a method of using a sparse aperture to construct an integrated detection device. By measuring the local wavefront at the seams and combining the wavefront reconstruction in the frequency domain, we can finally achieve the co-focus and co-phasing state testing of large-aperture segmented telescopes. Based on simulation analysis, the accuracy of the overall wavefront reconstruction (18 sub-mirrors) of our system is better than 0.01λ (λ stands for wavelength). Regarding the measurement and control accuracy of a single discrete aperture, on the basis of camera alignment, we conduct large-range feedback based on dispersion fringes and achieve precise co-phasing and accuracy verification based on the wide-band method. Ultimately, the closed-loop stabilization accuracy of the system in a non-vibration-isolated environment is better than 0.097λ. For spectral response testing, we use a split-type small-aperture integrating sphere to achieve a spectral splicing measurement of a large-aperture telescope. For an experimental system with an focal ratio of 10, the fluctuation of the light-intensity contrast in each field of view is better than 4%. Due to its small size and light weight, the proposed system can be used not only for integrated inspection in the manufacturing phase, but also for accuracy verification during on-site assembly and system calibration during operation intervals.

A distributed optical fiber sensing system composed of communication optical cables, strain optical cables, and a Brillouin optical time-domain reflectometer is adopted to conduct long-term monitoring of the slope stability of open-pit mines. By optimizing the trench structure design, anchoring system, and optical cable laying path, the optical cable deployment for 10 km, 3300 m, and 3500 m of the open-pit mine slope is completed, establishing a distributed monitoring engineering verification system for open-pit mine slopes. The research results show that through reasonable engineering design and control of the test parameters of the Brillouin optical time-domain reflectometer, long-distance, continuous, real-time, and large-scale distributed monitoring can be achieved; rock and soil masses, anchor rods, and strain optical cables can achieve a better coupling effect, which can realize the spatial?temporal continuous perception of surface and internal deformation of open-pit mine slopes. This method provides valuable insights into the deformation behavior of rock and soil mass slopes. In the future, by combining this monitoring technology with methods such as numerical simulation, potential landslide risks can be effectively and timely identified, and necessary measures can be implemented to ensure the stability of the slope.

To address the challenges associated with methane gas leak monitoring and localization in oil and gas pipelines, and to overcome the limitations of existing laser-based point measurement techniques, this study proposes a novel dual-band short-wave infrared (SWIR) gas detection technology based on differential ratio spectral imaging. The system locks the laser output at a central wavelength specific to methane detection and controls the laser beam scanning trajectory and direction in real time through an adjustable beam scanning module. By integrating laser absorption spectroscopy with a shortwave infrared camera, spectral information from both absorption and non-absorption regions is captured to generate intensity images of methane gas at varying volume fractions under specific laser wavelengths. Through the application of image processing algorithms, differential ratio analysis is conducted between the methane absorption band (1653.72 nm) and two adjacent non-absorption bands (1653.82 nm and 1653.62 nm), effectively eliminating background radiation interference in methane gas plumes and distinctly visualizing the intensity distribution of methane volume fractions. Experimental validation using standard gas bags to simulate methane leak scenarios demonstrates the feasibility of this approach, with processed image intensity to establish a calibration curve correlating the dual-band differential ratio with gas concentration path length, enabling quantitative detection and analysis. This imaging methodology effectively mitigates the drawbacks of conventional measurement techniques, such as measurement point deviation and the inability to achieve quantitative assessment, thereby providing a robust and precise approach for applications including methane cloud distribution mapping in mining operations and methane leak detection in oil and gas fields.

To address the issue of decreased signal-to-noise ratio in Doppler signals when using a laser Doppler velocimeter for high-speed carrier velocity measurements, this study analyzes the impact of pre-amplifier circuit output noise on Doppler signal quality. Theoretical analysis and simulation results indicate that the noise gain peak in the pre-amplifier circuit significantly affects the signal-to-noise ratio of Doppler signals, particularly at high frequencies, leading to a reduction in signal-to-noise ratio. Two types of operational amplifiers are selected to design the pre-amplifier circuit, and their respective output noise and signal-to-noise ratio are analyzed. Experimental validation of the simulation results demonstrates that selecting appropriate electronic component parameters can mitigate the effect of the noise gain peak on the signal-to-noise ratio of Doppler signals. This provides theoretical support for optimizing the pre-amplification circuit design of laser Doppler velocimeters, enhancing their suitability for high-speed carrier velocity measurements.

To enhance the localization capability of Brillouin optical time-domain reflectometry (BOTDR) for weak temperature variations along optical fibers, a method based on Brillouin frequency shift (BFS) fluctuation calculation is proposed. This method uses the BFS of a temperature-invariant fiber as a baseline, which is processed via sliding averaging to establish a reference benchmark. The measured BFS data under temperature variation undergoes identical processing and is then compared pointwise with the benchmark. This enables the localization of weak frequency shift points and the inference of their corresponding temperature variation ranges. Experimental results demonstrate that, without adding any additional hardware components to the system, the proposed method successfully identifies minute temperature change regions of 0.5 ℃, leading to improved system performance.

This research aims to provide a rapid, non-destructive solution for monitoring ionic liquid mass fraction in pharmaceutical production by proposing and validating a systematic chemometric modeling framework based on near-infrared (NIR) spectroscopy. The study first identifies 1350?1650 nm as the optimal analytical band through spectral mechanism analysis. Subsequently, based on the spectral data of 59 ionic liquid samples, the efficacy of various preprocessing and feature selection algorithms is systematically compared. Standard normal variate (SNV) is identified as the optimal preprocessing method, and competitive adaptive reweighted sampling (CARS) is determined to be the superior feature selection algorithm. The final SNV-CARS-PLSR quantitative model, integrated with partial least squares regression (PLSR), demonstrates excellent predictive performance: a root mean square error of calibration of 0.0689, a calibration determination coefficient of 0.9836, a root mean square error of prediction of 0.1008, and a prediction determination coefficient of 0.9666. To verify the universality of this methodological framework, it is further applied to a quantitative analysis of a glucose aqueous solution system, which also achieves outstanding prediction accuracy (0.9993). The systematic optimization strategy established in this study not only provides robust technical support for the real-time monitoring of ionic liquids but also offers a versatile methodological reference for the application of micro-NIR spectroscopy in the fine chemical industry.

Traditional remote sensing imaging for marine oil spills faces challenges such as high sensitivity to lighting conditions, low oil?water contrast, and significant surface glare interference. To address the resulting degradation in imaging quality and reduced accuracy of monitoring systems, this study employs four imaging modalities—visible light, visible light polarization, near-infrared, and long-wave infrared—to conduct outdoor field experiments under three high-interference scenarios (strong light, weak light, and sun glint conditions) from the perspective of oil spill imaging channel selection. By comparatively analyzing the information entropy and strong edge width of oil spill images across the four imaging modes, the study verifies the feasibility of using visible light polarization imaging under strong/weak light and sun glint conditions, and near-infrared imaging under strong light and sun glint conditions for oil spill detection. Meanwhile, experiments demonstrate that long-wave infrared exhibits limited effectiveness for thin oil film detection under weak illumination or sun glint conditions. This research provides experimental evidence for selecting optimal information channels in marine oil spill monitoring systems.

In the field of distributed optical fiber sensing technology, the application of the Brillouin scattering based optical time domain analysis system (BOTDA) in infrastructure structure health monitoring (SHM) has shown large-scale development, and the monitoring demand for the distribution of strain and temperature changes along or within engineering structures is increasing. The single-ended BOTDA system, with the convenient usage mode of single-end access of the sensing optical cable and combined with its own advantage of high-precision measurement, has won the favor in the engineering application field. In this paper, the development of single-ended stimulated Brillouin scattering fiber sensing technology is studied and summarized, the principle and characteristics of the single-ended BOTDA system based on Fresnel reflection and Rayleigh scattering are expounded, and the technical research of these two types of systems is subdivided, while the core content of each technical route is analyzed and discussed, such as heterodyne detection technology and multi-wavelength technology. Compared with the traditional double-ended access system, these types of single-ended BOTDA show different degrees of improvement in terms of simplifying the system structure, shortening the algorithm demodulation time, and reducing the frequency sweep times in addition to the advantages of single-ended access systems. Through the comprehensive analysis of related achievements and research progress, it is expected to further promote the in-depth research of high-performance single-ended BOTDA technology and its extended application in various related engineering fields.

Integrated circuit (IC) manufacturing technology is the foundation of modern society. Accurate fabrication of chip design patterns faces challenges in pattern resolution, layer-to-layer overlay accuracy, and manufacturing yield. In particular, overlay error in IC manufacturing has been the critical factor for chip yield improvement. It is crucial for engineers to gain a comprehensive understanding of overlay errors, including their causes, measurement methods, feedback algorithms, and control elements. This review examines the technical challenges in chip manufacturing overlay alignment, particularly focusing on advanced process requirements for overlay error specifications. We address issues such as process variations leading to decreased overlay precision, reduced measurement accuracy, and increased difficulty in matching error control. The paper systematically analyzes methods and algorithms for improving overlay accuracy and control quality. These include measurement techniques, compensation models, mark selection, artificial intelligence integration, and self-aligned processes. By examining the relationship between process variations and chip overlay errors, this review provides valuable references for China's IC equipment and process development, aiming to enhance chip manufacturing yield through multi-factor collaborative development.

In recent years, researchers have integrated various detection mechanisms and investigated a series of optoelectronic detection technologies, aiming at online monitoring of hydrogen leakage in sealed hydrogen storage devices and hydrogen pipelines. This review categorizes direct and indirect detection methods and introduces recent advancements in detection technologies for hydrogen storage and transportation infrastructures. We conduct a comparative analysis to summarize the features and merits of each technology. Finally, we predict the prospects for the further development of optoelectronic detection technologies for the safe operation and maintenance of hydrogen storage and transportation systems.

To achieve higher accuracy in distortion correction with a limited number of marking points, we propose a method for optimal arrangement of marking points and reverse fitting distortion correction based on Zernike polynomials. In this method, we do not directly obtain the distortion distribution by fitting the position errors of marking points in the measurement results. Instead, we first fit the distortion errors based on the true positions of the components and then recover the distortion distribution through a reverse solution, which effectively avoids high-order errors introduced by the distortion itself. Additionally, we establish an algorithm for solving the marking point distribution by minimizing the matrix condition number and obtain the optimal arrangement coordinates for marking points based on Zernike polynomials. Compared with traditional methods, our proposed method improves the correction accuracy by more than 7 times with fewer marking points. This method has been successfully applied in the testing and processing of a Φ150 mm double-curvature elliptical mirror (asphericity of 8.86 mm, maximum distortion of 79 mm), achieving an average correction accuracy of 0.252 mm. The final surface accuracy, represented by the root mean square (RMS) error, reaches 0.029λ, which strongly supports the manufacturing of important optical components.

The event camera is a biomimetic dynamic vision sensor with advantages such as high time resolution, wide dynamic response range, and low power consumption. It can continuously capture changes in light intensity within the field of view. Developing visual measurement solutions based on event cameras is crucial for addressing dynamic problems. However, event-based measurement systems face two significant challenges. Firstly, event cameras output asynchronous event streams, which lose spatial information during transmission, making it difficult to reference traditional vision measurement algorithms. Secondly, event cameras lack reliable filtering algorithms, leading to poor-quality restored event frames, which are insufficient for reliably calculating image features. Our study outlines the development process of event cameras and reviews research on event-based target tracking. We also discuss advancements in event camera calibration, event-based structured light measurement, and event-based autofocus techniques. The 3D measurement scheme based on event cameras encounters issues with the unreliability of event stream data features and low measurement accuracy. By studying spatio-temporal information extraction algorithms, we aim to improve measurement accuracy. Developing high-speed event camera measurement systems and designing efficient solutions with low-bandwidth, low-power, and small computation will further advance the field of high-speed visual measurement.