The accurate identification of historical restoration traces and material degradation is essential for the scientific preservation of ancient bronzes. In this study, the prestigious FUHAO bronze artifact (late Shang period, 13th-11th century BCE) was non-destructively examined using pulsed thermal imaging (PT). By combining single- and double-layer heat conduction models with Thermal Tomography (TT), this approach allowed for precise spatial localization of repair crevices, patches, and filler materials, while also distinguishing restorative interventions from the original bronze substrate. The artifact was revealed to have been assembled from multiple fragments, exhibiting uneven surface corrosion and clear evidence of prior conservation. The results not only provide direct insights for conservation strategy and historical interpretation but also demonstrate the capability of pulsed thermal imaging as an effective diagnostic tool for the integrated surface and subsurface assessment of cultural heritage objects.

[Objective]In response to the strategic demands of national ecological civilization,meteorological observation lidar,as a key technology for atmospheric environmental monitoring,has become a core support for promoting the high-quality development of the meteorological industry.To address the challenges of high cost,high risk,and difficulty in reproducing experimental phenomena in traditional practical teaching,this study aims to develop a virtual simulation experimental system for meteorological observation lidar,thereby compensating for the shortcomings of existing virtual simulation systems in meteorological remote sensing.The system is developed based on a national first-class course and the Lidar Remote Sensing Research Center at the Xi'an University of Technology.It is designed to enhance students'comprehensive design and innovation capabilities and to provide core teaching support for cultivating high-level interdisciplinary meteorological talents in the new era.[Methods]This study adopts an experimental approach based on"modular design and progressive training"and constructs a three-tiered experimental framework comprising"cognition,design,and exploration,"corresponding to three core modules:lidar system cognition,multispectral spectroscopic system design,and detection and data processing.(1)At the cognitive level,students master the structure and principles of lidar systems via immersive navigation and interactive model demonstrations.(2)At the design level,a task-driven mode is adopted to enable students to independently select detection targets and complete the design of a multispectral spectroscopic system.(3)At the exploration level,students assemble a functional lidar system and undergo a comprehensive training in data acquisition,inversion,and systematic error analysis.Throughout the experiment,scientific methods—including observation,modeling,comparison,and induction—are seamlessly integrated,with theoretical knowledge embedded into interactive tasks,thereby effectively enhancing the students'capabilities from basic cognition to comprehensive innovation.[Results]This study has achieved substantial teaching effectiveness through an innovative design that integrates science and education,virtual reality,and learning with assessment.The system employs high-fidelity modeling to authentically reproduce lidar structures and detection processes,effectively addressing the challenges of high cost,safety risks,and limited repeatability in traditional experimental teaching.Within the simulated environment,students engage in a complete workflow,including system cognition,optical design,data acquisition,and inversion analysis.Their operational behaviors are recorded in real time and automatically evaluated,generating comprehensive multidimensional assessment reports.The experiment thus achieves a deep integration of theoretical knowledge acquisition,practical skill training,and process-oriented evaluation.[Conclusion]The implementation of this study has not only advanced the systematization and practical application of virtual simulation experiments for meteorological observation lidar,but has also explored an innovative talent development pathway characterized by"virtual augmentation of real practice and the integration of science and education."This experimental framework significantly enhances students'capabilities in system design,data processing,and scientific inquiry in complex meteorological detection scenarios.It provides robust support for cultivating high-quality talents in emerging engineering majors such as instrumentation,optoelectronics,and meteorology,thereby offering an important teaching and practical platform for the independent development of meteorological detection equipment and technologies in China.

This paper presents a method for estimating significant wave height (Hs) from sparse S_pectral P_oint using a T_ransformer-based approach (SPT). Based on empirical observations that only a minority of spectral points with strong power contribute to wave energy, the proposed SPT effectively integrates geometric and spectral characteristics of ocean surface waves to estimate Hs through multi-dimensional feature representation. The experiment reveals an intriguing phenomenon: the learned features of SPT align well with physical dispersion relations, where the contribution-score map of selected points is concentrated along dispersion curves. Compared to conventional vision networks that process image sequences and full spectra, SPT demonstrates superior performance in Hs regression while consuming significantly fewer computational resources. On a consumer-grade GPU, SPT completes the training of regression model for 1080 sea clutter image sequences within 4 minutes, showcasing its potential to reduce deployment costs for radar wave-measuring systems. The open-source implementation of SPT will be available at https://github.com/joeyee/spt

Aimed at the susceptibility of traditional contact temperature sensors used for point air temperature measurements in meteorological stations to environmental radiation, a radiation-insensitive precision measurement method for absolute temperature of point air based on high-spectral-resolution lidar (HSRL) is proposed and demonstrated. By utilizing the correlation between the Rayleigh scattering spectrum distribution and temperature, the point air absolute temperature can be accurately retrieved by scanning the atmospheric molecular scattering spectrum distribution with Fabry-Perot interferometer (FPI). A lateral scattering scanning HSRL is designed specifically for measuring point air absolute temperature. The scanning frequency range is set at 10 GHz with a scanning period of 9.749 s. Experimental data are collected to obtain scattering spectra at various temperatures. The air temperature is retrieved through data processing techniques, including noise filtering, periodic superposition, Mie scattering correction, and deconvolution. By comparing the analytical G3 model and the kinetic Tenti-S6 model, the Tenti-S6 model is selected as the temperature-retrieval model owing to its smaller spectral residuals. Compared with readings from a co-located, the thermobarometer used only as an external reference for validation, the proposed method achieves a mean absolute error (MAE) of 0.74 K, and the root-mean-square error (RMSE) between the measured scattering spectra and the Tenti-S6 model is 0.0081 in intensity. These results demonstrate the feasibility of HSRL-based point air absolute temperature retrieval and provide a basis for extending the technique towards traceable meteorological temperature measurements and future atmospheric temperature profiling.

Accurate measurement of atmospheric temperature profiles in the mesopause region is crucial for understanding the atmospheric dynamics and climate processes. To address this challenge, a sodium Doppler lidar based on the resonance fluorescence scattering mechanism was recently developed to precisely detect atmospheric temperatures in the mesopause region in Qingdao (36.1°N, 120.1°E), China. For the first time, high-resolution observations of atmospheric temperature in the mesopause region (80–105 km) were achieved by the self-developed Na Doppler lidar in Qingdao under the complex atmospheric conditions of the mid-latitude coastal zone. A systematic cross-validation between the self-developed lidar and SABER satellite observations was conducted, and the temperature bias between the two detection methods in the mesopause region and its altitude-dependent characteristics were quantitatively assessed. The temperature profiles measured by lidar exhibited good agreement when compared with the satellite data yielding estimations of RMSE and mean absolute deviation of 9.2 K and 7.3 K, respectively, from 80 km to 100 km altitudes. A correlation analysis conducted between the lidar temperature data and satellite data showed that the closer the satellite passed over Qingdao, the better the correlation demonstrated by the data. The correlation coefficient of the closer comparison data can reach 0.86, which means that the self-developed lidar system in Qingdao has a good ability to detect temperature profiles in the middle and upper atmosphere. The nocturnal evolution details and short-period fluctuations of the temperature field in the mesopause region over Qingdao were observed, revealing the local temperature structural characteristics under the complex atmospheric conditions at the land–sea interface in the Qingdao area.

Objective Wind fields are one of the fundamental parameters used to describe atmospheric conditions, and high--precision observational data on wind fields serve as an essential foundation for meteorological analysis, climate research, wind energy resource assessment, aviation and maritime safety, environmental monitoring and early warning, as well as studies on plant pollination and seed dispersal. Common methods for wind measurement currently include cup anemometers, weather balloons, Doppler weather radars, and Doppler wind lidars. Compared with other wind measurement techniques, Doppler wind lidar has advantages such as high measurement accuracy, high sensitivity, and high spatiotemporal resolution. However, traditional spatial incoherent Doppler lidar suffers from limited stability due to its complex structure, while all--fiber coherent wind measurement systems are constrained by their reliance on aerosol scattering signals, restricting detection to low altitudes. Therefore, the development of a next generation system that is compact, highly stable, highly sensitive, and capable of measuring the full-scale wind field from low to high altitudes has become an urgent priority. Methods A fully fiber--based incoherent Doppler lidar system was designed, with its core composed entirely of fiber-optic components including a fiber laser, a fiber circulator, and a fiber Mach-Zehnder frequency discriminator. The 532 nm pulsed laser output from the fiber laser is split into two beams by a 1 & times;2 fiber coupler. A small portion of the laser serves as a reference signal and is directed straight into input port 1 of the fiber optic Mach-Zehnder interferometer to calibrate laser frequency drift and energy fluctuations. The majority of the laser is transmitted into port 1 of the fiber circulator, exits from port 2, and is then sent through a telescope into the atmosphere. The backscattered atmospheric signal is collected by the telescope, transmitted via port 2 of the fiber circulator to port 3, and enters input port 2 of the fiber optic Mach-Zehnder interferometer. The two interference outputs of the fiber optic Mach-Zehnder interferometer are detected by photodetectors, and the data are processed and inverted to obtain the line--of--sight wind velocity. First, numerical simulations were conducted to analyze the effects of parameters such as laser energy, pulse repetition frequency, telescope aperture, pulse accumulation number, arm length difference of the frequency discriminator, and pulse linewidth on the system's detection performance and sensitivity, thereby determining the optimal design parameters of the system. Second, a temperature control system was introduced to precisely regulate the arm--length difference, ensuring that the system consistently operates at its optimal working point. Subsequently, a reference signal was used for zero--wind calibration, enabling real-time compensation of wind measurement errors caused by frequency drift of the laser itself. Finally, an experimental platform was constructed, and calibration experiments were conducted using a turntable to simulate wind speed, in order to validate the effectiveness of the temperature control and frequency correction techniques. Results and Discussions Simulation results indicate that, under the conditions of a laser energy of 1 mJ, a pulse repetition frequency of 1 kHz, a telescope aperture of 1 m, a cumulative number of received pulses of 10(6), a frequency discriminator arm--length difference of 0. 75 m, and a laser linewidth of 100 MHz, the fully fiber--based incoherent Doppler lidar system achieves optimal detection performance. Specifically, under a daytime solar background radiation intensity of 1.75 W center dot(m(2) center dot sr center dot nm)(-1), the maximum detection range reaches 6.97 km, whereas at night, when the background radiation intensity decreases to 10(-5) W center dot(m(2)center dot sr center dot nm)(-1), the detection range extends to 23.66 km. When the temperature control system together with the heating film stabilized the interferometer arm at 31.4 degrees C , the frequency discriminator was locked at its optimal working point with the highest sensitivity. After performing zero-wind calibration using a reference signal, wind measurement errors caused by intrinsic frequency fluctuations of the laser were effectively eliminated. Finally, a turntable was used to generate controllable rotational speeds, and the resulting small Doppler frequency shifts produced significant variations in transmission intensity, which were used to retrieve the simulated wind speed. Without calibration, the measured wind speeds deviated substantially from the corresponding turntable values, with an average error of 0.76 m/s. After calibration, the wind speed errors were significantly reduced, showing closer agreement with the actual wind speeds, with an average error of 0.24 m/s. Overall, the retrieved wind speeds were in good agreement with the set wind speeds. Conclusions The above study not only demonstrated the technical feasibility of the fully fiber--based incoherent Doppler lidar but also highlighted its significant advantages and value in the field of wind measurement. This research provides a solid theoretical foundation and a systematic technical framework for the future development of wind--measuring radars toward compactness, lightweight design, and large-scale detection.

To meet the requirements of three-dimensional wind field detection using incoherent Doppler lidar, a scheme based on beam deflection by a wedge prism is proposed. By precisely controlling the laser pointing, multiple azimuth radial wind speed data can be synchronously obtained in a single scan. Combined with the incoherent Doppler wind detection principle and the four-beam DBS Doppler vector wind reconstruction algorithm, high spatiotemporal resolution three-dimensional wind field reconstruction is achieved. A wedge prism system was designed, an error pointing model was established, and the influence of individual errors on wind speed and wind direction was quantitatively analyzed, with corresponding solutions proposed. A three-dimensional wind field detection system based on a fiber Mach–Zehnder interferometer discriminator was built, achieving three-dimensional wind field detection within a range of 2.5 km. The experimental results were analyzed and compared with the zonal wind (U component) and meridional wind (V component) from ECMWF ERA5 reanalysis data. The results show that the wind speed measurement error is 0.39 m/s and the wind direction error is 4.37°, effectively meeting the application requirements for high-resolution three-dimensional wind field detection.

A large luminous flux 2 pi-LED total luminous flux standard lamp (2 pi-LED standard lamp) based on the 200 LED chips arranged in a rectangular structure and cooled by a thermoelectric cooler (TEC) is reported. The overall size of the 200 LED chips is 167.9 mm x 78.6 mm. Under the conditions of the driving voltage is 52.5 V, the current is 1.4125 A, the TEC cooling temperature and the ambient temperature are set to 25 degrees C, the total luminous flux of the 2 pi-LED standard lamp exceeds 10000 lm, the luminous efficiency reaches 135.3 lm/W. The photometric instability and non-repeatability are only 0.07% within 200 h and 0.04%, respectively. The deviation between the luminous intensities at different angles is 2%, and the colour space uniformity is 0.001. This type of standard lamp has important application for improving the efficiency and reliability of the traceability of photometric parameters such as total luminous flux, illuminance, and luminance of a high-power 2 pi-LED lighting.

A quadri-channel Mach-Zehnder interferometer (QMZI) with periodic transmittance is developed as the spectral discriminator for multi-longitudinal-mode incoherent Doppler wind lidar (MLM IDWL), which can be applied to measure atmospheric wind ranging from low altitudes using aerosol Mie scattering signals to high altitudes using molecular Rayleigh scattering signals. The key to achieving high-precision atmospheric wind measurement for MLM IDWL is to ensure the matching between the MLM laser spectra and the QMZI transmittance curve. However, the Gaussian distribution characteristics of the MLM laser inevitably introduce a divergence angle into the input signals of QMZI, causing the mismatch between the MLM laser spectra and QMZI transmittance curve, and degrading measurement performance. To address this problem, considering the divergence-angle-induced spectral mismatch, the wind inversion algorithm and performance evaluation parameter models are quantitatively developed for the MLM IDWL, and the effects of the divergence angle are analyzed through theoretical simulations and optical ray-tracing simulations. To mitigate this mismatch, a field-widening technique is introduced, using compensated glass with high refractive index, high transmittance, and high stability. The model-based quantitative analysis shows that the proposed field-widening compensation can effectively expand the field of view of the QMZI from 0.4 mrad to 10.0 mrad, thereby significantly enhancing the measurement performance of the MLM IDWL.

Multi-longitudinal-mode (MLM) high-spectral-resolution lidar is a new concept of incoherent Doppler wind lidar (IDWL), which can avoid the complex techniques of seed injection as well as the high requirement of frequency stabilization and frequency locking. To achieve high-precision atmospheric wind measurement, an optimized design is performed for the MLM IDWL, which utilizes a free-running MLM laser as the excitation light source and a quadri-channel Mach-Zehnder interferometer (QMZI) as the spectral discriminator. Based on the partial coherence theory of quasi-monochromatic light interference, the data inversion algorithms for MLM IDWL are simplified, and the performance evaluation parameters for MLM IDWL are analyzed. Furthermore, using the control variable method, the key parameters of MLM IDWL are optimized by discussing its performance evaluation parameters in the condition of aerosol Mie scattering or molecular Rayleigh scattering, respectively. The simulation experiments of wind measurement with the optimal key parameters prove that the MLM IDWL can realize the atmospheric wind measurement with an accuracy of 0.3 m/s in the low-altitude environments using aerosol Mie scattering echo signals and with an accuracy of 3.0 m/s in the high-altitude environments using molecular Rayleigh scattering echo signals.

Accurate measurement of propulsion generated by electrohydrodynamics (EHD) contributes to the assessment of the thrust efficiency of drones and electric aircraft and may provide benefits in sustainability and stability. Here, we propose an electrohydrodynamic (EHD) measurement system based on an optical Fabry-Perot (F-P) sensor which senses the EHD thrust generated by a bipolar corona discharge via an elastic sensitive element. Static calibration experiments of the sensor were performed under such a pin-plate corona discharge system. The dynamic output characteristics of the sensors were tested under corona discharges with different polarities and discharge distances. The results show that the sensor has a linear operating region of 4-7 kV, a linearity of 99.6%, and a sensitivity of 257.7 pm/kV. Negative corona discharge leads to a higher spectral offset of the sensor compared with positive corona discharge. Continuous and simultaneous ionic wind sensing via an optical EHD sensor should provide accurate information about the performance of the propulsion system and contribute to the enhancement of the dynamic stability of the EHD actuator system.

An autocollimator is a popular angle measuring apparatus which lacks the capability to measure the roll angle. This paper proposes a novel roll angle sensor with a large measuring range that is based on the autocollimation principle. A modified right-angle prism (MRP) functions as a reflector to admit a collimated beam and return two outgoing beams to the sensor head. The roll angle of the MRP can be attained by analyzing the moving tracks of the two light spots focused on a photodetector. The mathematical model is derived in detail, and the experimental results show that the measuring accuracy of the proposed sensor is ±13.85 arcsec over a range of 360°. These results verify the feasibility of the proposed sensor for roll angle measurements that require a large measuring range.

An autocollimator is a goniometer established according to the principle of autocollimation, but it is ineffective for measuring the roll angle. This paper proposes an improved autocollimator available for large-range roll angle measurement, which maintains the optical structure of the classic one while incorporating a wedge prism (WP) working in transmissive mode as a roll angle sensing element to dissociate the collimated beam into two beams. According to the moving paths of the two light spots focused on the photodetector, the roll angle of the WP can be solved. The measuring method is expounded, and the calibration results reveal that the improved autocollimator has an accuracy of ±13.55 arcsec over a range of 360°, confirming its feasibility for roll angle measurement where a large measuring range is required.

The roll angle is an important albeit difficult-to-measure geometric parameter. This study proposes a roll angle measurement method for an entire circle (360°). An elaborately designed double-sided optical wedge (DOW) is employed as a roll angle probe to divide the incident light beam into two beams. Both beams are imaged using a photodetector, and the roll angle of the DOW is obtained through the detection of the motion trajectories of the two images. The measurement principle is comprehensively analyzed, and the experimental results indicate that the accuracy of the constructed measurement system is better than ±7.72arcsec in the range of 360°. The proposed method is confirmed to be effective for large-range roll angle measurements.

Among the various methods for detecting electrostatic discharge, optical electrostatic sensors have attracted widespread attention due to their numerous advantages, such as high sensitivity and rapid response capabilities. As a type of optical sensor, the performance of fiber-optic F-P electrostatic sensors will be affected the design of the collector. Therefore, a detailed study of the collector design in F-P electrostatic sensors is crucial for enhancing the precision and reliability of electrostatic discharge measurements. In this paper, the sensing capabilities of sensors with equilateral triangular, square, and circular collectors of identical areas under external applied voltage are tested. Simultaneously, models of these three shaped collectors are constructed and subjected to simulation analysis. Experimental results demonstrate that the cavity drive displacement of the sensor with a circular collector exhibits a good linear relationship with the applied voltage. The results also indicate that circular collector, compared to square and equilateral triangular ones, are more suitable for use as sensing modules in sensors. This research provides meaningful insights for the design and optimization of these sensors.

Single-longitudinal-mode (SLM) direct Doppler wind lidar (DDWL) requires complex techniques of the seed injection, high precision frequency stability, and frequency locking to provide an output of the stable frequency SLM laser, resulting in a complex structure of DDWL. To reduce the technical difficulty and structural complexity of the excitation light source of DDWL, a multi-longitudinal mode (MLM) DDWL is proposed. In the MLM DDWL, a free-running MLM laser is directly used as an excitation light source and quadri-channel Mach-Zender interferometer (QMZI) with four periodic outputs is adopted as a spectral discriminator. Firstly, for the typical Nd:YAG pulsed laser, the scattering spectra of atmospheric elastic echo excited by the MLM laser are analyzed which are coincident with the longitudinal modes of the MLM laser. The peaks of atmospheric elastic echo scattering spectra excited by the MLM laser overlap with each other. The overlapping degree is affected by the laser radiation linewidth, laser optical resonator length, laser center wavelength, and type of scattering particles. In addition, the scattering spectra of atmospheric elastic echo excited by each longitudinal mode of the MLM laser have the Doppler frequency shift introduced by atmospheric wind. Therefore, it is necessary to select an optical interferometer with the periodic transmittance curve as the spectral discriminator of MLM DDWL. Subsequently, a QMZI is designed as the spectral discriminator to achieve high-precision measurement for the Doppler frequency shift of scattering spectra of atmospheric elastic echo excited by the MLM laser. The designed QMZI has four periodic output channels and the phase difference between adjacent channels is pi/2. The mathematical model of the transmittance function of the QMZI is established. The effective transmittance of the QMZI for atmospheric elastic echo scattering spectrum excited by the MLM laser is analyzed based on the partial coherence theory of quasi-monochromatic light interference and the polarization effect of light. On this basis, the data inversion algorithm of MLM DDWL is constructed. Finally, the simulation experiments of wind measurement are carried out. The QMZI simulation model is built by the non-sequential mode of Zemax optical simulation software. The atmospheric elastic echo scattering spectra excited by the MLM laser are configured by the SPCD files of Zemax optical simulation software under different theoretical wind speeds ranging from -50 to 50 m/s, laser optical resonator lengths (L = 30 mm and 300 mm), and laser center wavelengths (A = 1064, 532, and 355 nm). The SPCD files are fed to the QMZI simulation model as input signals. At the same time, the ray tracing on input signal is performed based on the principle of Monte Carlo simulation s, and the output signals of the four channels of the QMZI simulation model are recorded to retrieve the atmospheric wind information. The simulation results show that the proposed MLM DDWL can achieve high-precision measurement of atmospheric wind information. With the laser optical resonator length of 300 mm and laser center wavelengths A = 1064 nm, A = 532 nm, A = 355 nm, the maximum detectable wind speeds of MLM DDWL are about 50, 30, and 20 m/s, and the wind measurement errors can be controlled within 2.5, 3.0, and 4.0 m/s, respectively. When the center wavelength of each laser is 532 nm, and the lengths of laser optical resonator are 30 mm and 300 mm, then the maximum detectable wind speeds of MLM DDWL are about 50 m/s and 30 m/s, and the wind measurement errors can be controlled within 2.0 m/s and 3.0 m/s, respectively. Therefore, the longer the laser center wavelength and the shorter the laser optical resonator length, the larger the wind measurement range will be and the smaller the wind measurement error.

Optical electrostatic sensors play an essential function in the development of digitalization and intelligence of power systems due to their passive, anti-electromagnetic interference, and fast response speeds. However, the performance of optical electrostatic sensors is affected by the collector size. In this paper, the dynamic output characteristics of fiber optic electrostatic sensors with different collector sizes are tested. Meanwhile, models of different sizes of collectors are also constructed and simulated and analyzed. The results show that the sensitivity of the sensor increases with the increase of the collector area. The sensitivity of the sensor with a 5 cm radius collector is 53.1 pm/kV. This study provides meaningful insights for the design and optimization of electrostatic sensors.

Objective More than 50% of atmospheric water vapor exists mainly in the lower atmosphere within 2 km. Vibrational Raman scattering lidar is an important remote sensing tool for atmospheric water vapor measurement. However, the traditional vibrational Raman scattering lidar mainly adopts a coaxial and non-coaxial parallel transceiver system structure, and the system detection blind zone and transition zone limit their effectiveness in ground atmospheric water vapor detection. We propose a novel detection technique of lateral vibrational Raman scattering lidars based on the structure of a bistatic system, where the lateral vibrational Raman scattering signals of N-2 and H2O at different heights are detected by the elevation angle scanning of the lateral receiver system. Finally, it realizes fine detection of near-surface atmospheric water vapor without a blind zone from the ground to the height of interest. Methods We study the lateral vibrational Raman scattering lidar technique in the application of accurate measurements of atmospheric water vapor from the ground to the height of interest. First, a novel lateral scanning vibrational Raman scattering lidar technique is proposed and designed. Two telescopes combined with specified narrow-band interference filters are utilized to detect the lateral scattering signals of the vibrational Raman scattering spectra of N-2 and H2O respectively. Then, the inversion algorithm of atmospheric water vapor using the lateral vibrational Raman scattering lidar is established. Vibrational Raman scattering spectra of N-2 and H2O have large wavelength differences, which lead to large differences between atmospheric transmissivity of the slant path in these two detection channels, and the aerosol extinction coefficients inverted by Raman method are adopted to correct atmospheric transmissivity of the slant path and improve the detection accuracy of the atmospheric water vapor mixing ratio. Finally, the construction of the experimental system is completed, and the preliminary experiments are conducted via the lateral scanning vibrational Raman scattering lidar. Two different rotation schemes including the continuous equidistant resolution and segmented equidistant resolution are employed during the experimental observations. Results and Discussions The detection principle of the lateral vibrational Raman scattering lidar is innovatively proposed. It breaks through the traditional backward vibrational Raman scattering lidar by a monostatic transceiver system structure, which produces the blind zone and transition zone without effective detection of near- surface atmospheric water vapor. Meanwhile, this technology can utilize a continuous-wave laser featuring light weight, portability, mobility, and low cost (Fig. 1). Data correction of atmospheric water vapor is realized by analyzing the atmospheric molecular scattering phase function and the difference in slant path atmospheric transmissivity caused by the wavelength difference between the vibrational Raman scattering spectra of N-2 and H2O. The aerosol extinction coefficient obtained from the inversion of the lateral N-2 vibrational Raman scattering signal is employed for real-time correction of the slant path atmospheric transmissivity, which improves the accuracy of atmospheric water vapor mixing ratio detection (Figs. 2-4). Preliminary experimental observational studies of a lateral scanning pure rotational Raman scattering lidar are performed by two different rotation schemes including the continuous equidistant resolution and segmented equidistant resolution, which are employed during the experimental observations. The experimental results show that both rotation schemes can realize atmospheric water vapor detection from the ground to the height of interest. In particular, the segmented equidistant resolution scheme can realize more fine detection of atmospheric water vapor distribution in the ground zone (Figs. 5- 8). Conclusions We focus on the detection demand for atmospheric water vapor from the ground to the height of interest using the lidar technique. Based on the theoretical basis of vibrational Raman scattering, the innovative technology of lateral scanning Raman scattering lidar for detecting atmospheric water vapor at the ground surface is proposed. This technology combines the elevation angle scanning function of the lateral receiver system to achieve non-blind scanning detection of water vapor in the lower atmosphere. Due to large differences between the wavelengths of the vibrational Raman scattering spectra of N-2 and H2O, the aerosol extinction coefficients obtained by inverting the lateral N-2 vibrational Raman scattering signals are adopted to make real-time corrections to the slant path atmospheric transmissivity, which improve the accuracy of atmospheric water vapor mixing ratio. If a high-power pulsed laser is applied, it can be simultaneously observed with a backward vibrational Raman scattering lidar to construct a joint detection system to realize the measurement of atmospheric water vapor from the ground to the height of interest. The experimental results show that the lateral vibrational Raman scattering lidar can detect atmospheric water vapor mixing ratios up to 1400 m with a horizontal distance of 60 m between the laser transmitter system and the lateral telescope receiver system. Additionally, the segmented equidistant resolution scheme has variable resolutions at different heights to show more details of water vapor distribution in the ground zone.

Given that plant leaves correspond to strong scattering media,a self-built Stokes polarization imaging system is used in this study to accurately describe the scattering characteristics of leaves.By further calculation of Stokes vector of plant leaves,the polarization uniformity of the physical quantity is used to systematically examine their polarization characteristics:1)the polarization characteristics of circularly polarized light and linearly polarized light on plant leaves are investigated,and it is determined that the polarization uniformity of leaves is higher under the incidence of linearly polarized light when compared to circularly polarized light;2)the dependence between the angle of leaf vein and direction of polarized light is examined,and it is determined that when the direction of linear polarized light is perpendicular to the angle direction of leaf vein,the polarization uniformity of leaf vein is the highest;3)the relationship between depolarization parameters and leaf water content is obtained.It is observed that as the leaf water content gradually decreases,the polarization uniformity of the leaf correspondingly increases.By examining the interaction between polarized light and plant leaves,this study demonstrates that polarization uniformity is a significant descriptor of leaf depolarization characteristics in response to polarized light.This insight lays a foundation for subsequent research into plant microstructure and growth state.

High-spectral-resolution lidar (HSRL) is a powerful tool for aerosol measurements. With/without laser seeding technique in the transmitted laser, the HSRL can be distinguished as the single-longitudinal-mode (SLM) HSRL or the multi-longitudinal-mode (MLM) HSRL, and the Mach-Zehnder interferometer (MZI) with periodic transmittance function can be used as the spectral discriminator in both the SLM HSRL and MLM HSRL. To in-depth knowledge of the respective advantages of the SLM HSRL and MLM HSRL for measuring aerosol optical properties, the working principle, optimal parameter setting, and detection performance of the SLM HSRL and MLM HSRL are analyzed and discussed in detail, respectively. The working principle of the SLM HSRL and MLM HSRL indicate that the effective transmittance of MZI is the important parameter of data retrieval, the main source of retrieval uncertainties, and the key factor of MZI optical path difference (OPD) settings. To ensure that the MZI can achieve the preferable separation for aerosol Mie scattering signals and molecular Rayleigh scattering signals, the optimal OPDs of MZI are set at 165 mm and 1000 mm in the SLM HSRL and MLM HSRL from the aspects of the effective transmittance of MZI and the spectral discrimination ratio (SDR). Besides, to analyze the influence of frequency difference and divergence angle for the detection performance of HSRL, the effective transmittance of MZI and SDR are simulated and the results show that the MLM HSRL has higher requirements for the environmental parameters and the echo beam collimation than the SLM HSRL. Moreover, the HSRLs with SLM and MLM transmitted lasers are constructed in Xi'an for measuring aerosol optical properties. The preliminary measurement results show that the range square corrected signal (RSCS) of Rayleigh channel is smaller than that of Mie channel in both the SLM HSRL and MLM HSRL, while the difference between RSCS of Rayleigh channel and RSCS of Mie channel in the SLM HSRL is larger than that in the MLM HSRL, and the detection range of the SLM HSRL is lower than that of the MLM HSRL.