Field Experiment of Hyperspectral Radiation Observation System
Yunfei Ma, Yakai Guo, Changliang Shao, Liying Liu, and Feng Li
To fill the gap in ground-based solar radiation observations in the existing meteorological business station network in China, we conducted two field experiments in Ewenki Autonomous Banner, Hulunbuir, Inner Mongolia in 2019 and 2022, using a domestic self-calibrating hyperspectral radiometer system. The results show that the monthly missing data rate of the system is less than 1%, and the mean time between failures reaches 96.5% of the effective working time, demonstrating its good stability in harsh outdoor environments. Compared with the corresponding products of broadband radiometers, the linear fitting coefficients of ultraviolet radiation, photosynthetically active radiation, total radiation, and direct radiation are 0.95, 0.97, 0.75, and 0.80, respectively. The linear fitting coefficient of hyperspectral direct irradiance of the proposed hyperspectral radiometer system is 97% compared with the products of the Japanese EKO hyperspectral radiometer, and the deviation of hyperspectral reflectance from the reference reflectance is less than 0.5%. These results indicate that the domestic hyperspectral radiometer system operates stably, and its data product accuracy is comparable to that of international advanced solar hyperspectral observation products. It can provide strong support for improving China's ground-based solar radiation observation network and validating the products of meteorological satellite optical payloads, thereby significantly enhancing regional meteorological detection capabilities.
  • Aug. 25, 2025
  • Acta Optica Sinica (Online)
  • Vol. 2, Issue 16, 1615001 (2025)
  • DOI:10.3788/AOSOL250445
Fast Background Removal for Wide-Field Microscopic Imaging Defocus Signal (Invited)
Xinghao Li, Qianbo Liu, Yizhe Hao, Hao Xu, Wenhao Liu, and Weisong Zhao
Limited by the instrument structure of volumetric illumination, samples outside the focal plane of wide-field fluorescence imaging can be excited and generate fluorescent signals, forming a significant defocus background that seriously interference the image data analysis. To suppress the defocus signal in a single wide-field image, we propose an image restoration algorithm based on three-dimensional (3D) point spread function (PSF) estimation and deconvolution, which efficiently removes the defocus signal. Through the reconstruction of simulated multi-layer circular rings and 3D experimental imaging of cellular actin, we verify the superiority of the proposed method in enhancing image details and improving resolution, providing an effective solution for high-quality fluorescence imaging under a wide-field microscope.
  • Aug. 10, 2025
  • Laser & Optoelectronics Progress
  • Vol. 62, Issue 15, 1511002 (2025)
  • DOI:10.3788/LOP251069
Technical Issues and Challenges in In-Situ Infrared Spectroscopic Detection for Lunar Polar Regions (Invited)
Chengguang Li, Jinning Li, Zhendong Wang, Runfeng Zhang, Rui Xu, and Zhiping He
Exploring the distribution and state of resources in the lunar polar regions has become a hotspot in the current international lunar exploration field. China's Chang'e-8 mission requires in-situ infrared spectroscopic exploration of the lunar polar regions. However, the extreme environmental conditions in these areas such as low illumination and low temperatures pose numerous technical challenges for infrared spectroscopic detection. Regarding the current state of technology for in-situ spectral detection on the lunar surface, this paper specifically analyzes the major technical challenges faced in polar region exploration, and discusses potential solutions, aiming to offer theoretical and technical support for in-situ spectroscopic exploration of the lunar polar regions.
  • Aug. 10, 2025
  • Acta Optica Sinica (Online)
  • Vol. 2, Issue 15, 1512001 (2025)
  • DOI:10.3788/AOSOL250455
Inversion Method for Optical Parameters of High-Absorption Thin-Film Material Based on Reflection Spectra
Dong Li, Linghui Meng, and Jianxiao Liu
An inversion method for optical thin-film parameters based on reflection spectra is proposed, which does not require recording the phase and extremum of the reflection spectra. The complex refractive index and film thickness of optical thin films can be inverted using the reflectance amplitude, thus overcoming the disadvantage of existing techniques for measuring high-absorption thin films. This study analyzes reflection-spectrum data at different incident angles and uses the functional relationship among film reflectance, refractive index, and thickness to obtain the intersection points of reflection spectra in the refractive index-extinction coefficient planes at different incident angles. By integrating a global optimization algorithm, the refractive index and extinction coefficient values at various thin-film thicknesses for different wavelength nodes are solved. We identify the probability density distribution of the thin-film thickness corresponding to each wavelength node and utilize the results corresponding to the highest probability density of the most likely film thickness as the optimized thickness. Subsequently, a secondary inversion is performed to ascertain the optical parameters of the thin film. The proposed approach is applicable even when the optical characteristics of the material are unknown, as it does not necessitate fitting the material's refractive index. During the numerical-verification phase, the accuracy of the proposed method in inverting the optical parameters of high-absorption thin films is demonstrated via two computational examples. The proposed method provides a new practical tool for the development of optical thin-film technology, which is expected to promote its further application in multiple fields.
  • Aug. 10, 2025
  • Laser & Optoelectronics Progress
  • Vol. 62, Issue 15, 1531001 (2025)
  • DOI:10.3788/LOP242342
Research Progress on Single-Ended Stimulated Brillouin Optical Time-Domain Sensing Technology
Qingyu Xu, Dingyi Ma, Yongzheng Li, Linfeng Guo, and Xiaomin Xu
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.
  • Aug. 10, 2025
  • Acta Optica Sinica (Online)
  • Vol. 2, Issue 15, 1514001 (2025)
  • DOI:10.3788/AOSOL250459
Effect of Laser Forging on Microstructure and Mechanical Properties of Thin-Walled Parts
Hu Chen, Jiajie Li, Jingling Zeng, and Yongkang Zhang
To prepare high-quality aluminum alloy thin-walled parts and extend the service life of marine engineering equipments, the effect of laser forging composite arc additive manufacturing technology on the microstructures, porosities, and mechanical properties of thin-walled parts are studied. The results show that laser forging can effectively promote grain refinement, reduce the number and size of pores, and significantly improve the density of deposited layers and overall manufacturing quality. Microhardness and tensile experimental results show that, compared with thin-walled parts without laser forging process, the microhardness of the thin-walled parts with laser forging technology increases by 21.07%; landscape and portrait tensile strengths increase by 4.62% and 13.63%, respectively; and the elongation after breaking is also significantly improved. Therefore, laser forging can significantly improve the microstructures and mechanical properties of 5083 aluminum alloy thin-wall parts, providing an effective technical way for efficient repair and performance optimization of marine engineering equipment.
  • Aug. 10, 2025
  • Laser & Optoelectronics Progress
  • Vol. 62, Issue 15, 1514003 (2025)
  • DOI:10.3788/LOP242387
Specular Polarization-Based Surface Normal Imaging Technique
Yaru Gao, Hongning Li, Yangtao Xiang, and Jiacheng Wang
This paper proposes a specular reflection-based normal estimation method that employs polarization imaging to separate surface reflections into specular and diffuse components, achieving high-precision normal imaging. The imaging transition model is explored, an optimal strategy to determine the normal angle is discussed, and based on this, an active normal field imaging system employing a polarized LED light source is built and calibrated. Experimental results show that our method can measure surface normals with an MSE<0.7 (°)2 in a range from -25° to 25°. This imaging system is applied to investigate 14 different types of art paper. The results reveal that this method can effectively capture the normal variation of surfaces with low sensitivity to paper color. It also offers insights for the identification and restoration of calligraphy, paintings, and cultural relics.
  • Aug. 10, 2025
  • Acta Optica Sinica (Online)
  • Vol. 2, Issue 15, 1505001 (2025)
  • DOI:10.3788/AOSOL250467
Process Method of Small-Tool Polishing for Mid-Spatial Frequency Error Smoothing of Conical Surface Component
Hang Fang, Yuchuan Chen, Lin Zhang, Ye Ding, Kailong Li, Kuo Hai, and Yunfei Zhang
Currently, the conformal accuracy of small-tool smoothing polishing is low and does not satisfy the requirements of mid-spatial frequency (MSF) error smoothing. Hence, a small-tool polishing method for the MSF error smoothing of conical surface components based on a variable removal function is proposed. By performing theoretical modeling and finite-element simulation, the contact pressure distribution and the relative velocity model of conical surface components are established. Subsequently, based on Preston's equation, an annular removal function model is developed. By adopting the convolution principle and the constrained optimization algorithm, the dwell-time model for the small-tool polishing of conical surface components and its algorithm for conformal polishing are established. Small-tool polishing for the MSF error smoothing of conical surface components is investigated experimentally. The results show that the relative changes in the peak-to-valley value and root mean square are 13.7% and 9.3%, respectively, for a 310-mm-diameter conical mirror after smoothing. The peak value in the MSF band of the power spectral density curve decreased significantly, and the MSF error is effectively suppressed, thus confirming the correctness and feasibility of the proposed method.
  • Aug. 10, 2025
  • Laser & Optoelectronics Progress
  • Vol. 62, Issue 15, 1522001 (2025)
  • DOI:10.3788/LOP242316
Development and Prospect of High-Power Fiber Laser Chromatic Beam Combining Technology (Invited)
Wei Shi, Haibo Zhang, Junqing Meng, Bing He, and Xia Hou
The output power of a single-beam fiber laser has a theoretical limit, and high-power fiber laser beam combining technology is the key to achieving ultra-high power while maintaining high beam quality. This paper analyzes on the limiting factors for power increasing in high-power fiber lasers, and reviews principles, technical characteristics, and current technological statuses of different beam combining schemes. Among these, chromatic beam combining using dichroic mirrors demonstrates significant engineering advantages for power increasing and beam quality preservation in broadband laser systems. The paper reviews the developmental progresses in pulsed and continuous wave fiber laser chromatic beam combining technologies in both domestically and internationally, introduces key technologies and researches in this field. Finally, future prospects for chromatic beam combining technology are discussed.
  • Aug. 10, 2025
  • Laser & Optoelectronics Progress
  • Vol. 62, Issue 15, 1500006 (2025)
  • DOI:10.3788/LOP251119
Effect of Pulsed Laser Energy Density on Cleaning Quality of TA15 Titanium Alloy Oxide Film on Electrolytic Surface
Zhengyang Jiang, Dengyong Wang, Dongbao Wang, Piqing Xiao, and Yuanyuan Zhang
TA15 titanium alloy has excellent mechanical properties, but it is highly prone to passivation during electrochemical machining (ECM), forming an oxide film that hinders normal electrochemical dissolution, resulting in poor surface quality and high roughness. In this study, the oxide film on the electrolytic surface of TA15 titanium alloy is cleaned using an ultraviolet pulsed laser, and the effects of different energy densities on the microscopic morphology, elemental mass fraction, phase composition, and roughness of the cleaned electrolytic surface are examined. The experimental results reveal that the distribution of oxygen element on the electrolytic surface of the specimen is non-uniform, with the α-phase being prone to secondary oxidation at low optimal cleaning energy densities, and the β-phase, which has a higher oxygen mass fraction, requires higher energy densities for cleaning. In this study, the oxygen mass fraction of the two phases is balanced by applying the optimal energy density, resulting in lower oxygen mass fraction in both phases. The optimal cleaning parameter for the electrolytic surface oxide film is 2.39 J/cm2, at which the surface oxygen mass fraction decreases from the initial 33.17% to the minimum of 18.64%, whereas the titanium mass fraction increases from 51.65% to the maximum of 70.65%. The main component of the electrolytic surface oxide film is TiO2, and high energy densities also generate unstable suboxides Ti2O3 and TiO. As the energy density increases, the surface roughness (Ra) initially decreases and then increases, with the Ra value decreasing from the initial 4.92 μm to the minimum of 2.09 μm. The cleaned titanium alloy surface can also enhance the surface quality for subsequent ECM.
  • Aug. 10, 2025
  • Laser & Optoelectronics Progress
  • Vol. 62, Issue 15, 1514007 (2025)
  • DOI:10.3788/LOP242445