2024

• Record 133 of
  
  Title:Auto-Alignment Non-Contact Optical Measurement Method for Quantifying Wobble Error of a Theodolite on a Vehicle-Mounted Platform
  
  Author(s):Li, Xiangyu; Hao, Wei; Xie, Meilin; Liu, Bo; Jiang, Bo; Lv, Tao; Song, Wei; Ruan, Ping
  Source: TEHNICKI VJESNIK-TECHNICAL GAZETTE  Volume: 31  Issue: 2  DOI: 10.17559/TV-20230510000617  Published: 2024  
  Abstract:During non -landing measurements of a theodolite, the accuracy of the goniometric readings can be compromised by wobble errors induced by various factors such as wind loads, theodolite driving torque, and the stiffness of the supporting structure. To achieve high -precision non -landing measurements, it is essential to accurately determine and correct the platform wobble errors affecting the azimuth and pitch pointing angles. In this paper, a non -contact optical measurement method is proposed for quantifying platform wobble errors. The method establishes an auto -alignment optical path between an autocollimator and a reflector in the measuring device. By detecting the deviation angle of the CCD image point as the optical path changes, precise measurements of the platform wobble errors can be obtained. Experimental results demonstrate that the measuring device can achieve an auto -alignment optical path within 5 minutes, significantly improving measurement efficiency. Furthermore, after measuring the platform wobble error and applying data correction, the average error in the azimuth pointing angle is reduced from 31.5 '' to 9.8 '', and the average error in the pitch pointing angle is reduced from 21 '' to 9.2 ''. These results highlight the substantial correction effect achieved by the proposed method.
  Accession Number:
  ISSN: 1330-3651
  eISSN: 1848-6339
• Record 134 of
  
  Title:Efficient and high-spatiotemporal-quality terawatt-class mid-infrared optical parametric amplifiers by spatially shaped pumping
  
  Author(s):Liu, Xin; Li, Jinhui; Zhen, Qiwen; Liu, Keyang; Wang, Yishan; Zhao, Wei; Cao, Huabao; Fu, Yuxi
  Source: JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS  Volume: 41  Issue: 2  DOI: 10.1364/JOSAB.509609  Published: 2024  
  Abstract:We propose a method to efficiently generate terawatt (TW )-class mid -infrared (MIR) femtosecond laser pulses with high spatiotemporal quality through optical parametric chirped -pulse amplification (OPCPA). By transforming the pump -beam profile for the OPCPA from Gaussian to flat -top using a designed field mapping optics consisting of two aspherical lenses, we obtain a TW-class femtosecond laser pulse at 2 mu m with a conversion efficiency of over 36% according to our simulations. Furthermore, the spatiotemporal coupling effects are greatly suppressed in our method compared to an OPCPA system that is pumped by a widely employed Gaussian profile beam. Our work provides a simple and robust method for developing OPCPA systems with high efficiency and high pulse quality. (c) 2024 Optica Publishing Group
  Accession Number:
  ISSN: 0740-3224
  eISSN: 1520-8540
• Record 135 of
  
  Title:Accurate Real-Time Laser Spot Locating Based on Template Correlation in Intersatellite Laser Communications
  
  Author(s):Meng, Xiangsheng; Liu, Wen; Han, Junfeng; Tian, Yan; Liu, Jun; Ma, Caiwen
  Source: IEEE PHOTONICS JOURNAL  Volume: 16  Issue: 1  DOI: 10.1109/JPHOT.2023.3335234  Published: 2024  
  Abstract:In intersatellite laser communications, the centroiding accuracy of a laser spot is crucial for maintaining steady communication links. However, the systematic error introduced by discrete sampling restricts further improvement of centroiding accuracy when choosing algorithms that are widely used in engineering. Additionally, the ultrahigh computational complexity and multiple-step iterations of the Gaussian fitting (GF) algorithm are unsuitable for real-time implementation, even though the algorithm can achieve the highest centroiding accuracy. In this study, we propose a laser spot centroiding algorithm based on template correlation to simultaneously satisfy the requirements of real-time performance and accuracy. The proposed algorithm evaluates the central location of a laser spot by obtaining the index of the maximum Pearson correlation coefficient (PCC). Simulations performed under different conditions reveal that the proposed algorithm is robust against the interference of background noise and the bad pixels. Moreover, experimental verification is performed based on the implementation on a Field-Programmable Gate Array (FPGA) in real-time, meanwhile its accuracy is on the same level as that of the GF algorithm and better than those of other widely-used algorithms. Therefore, the proposed algorithm is suitable for accurate real-time locating of laser spots in engineering applications of the intersatellite laser communications.
  Accession Number: 7800209
  ISSN: 1943-0655
  eISSN: 1943-0647
• Record 136 of
  
  Title:Repetition rate tuning and locking of solitons in a microrod resonator
  
  Author(s):Niu, Rui; Wan, Shuai; Sun, Shu-Man; Ma, Tai-Gao; Chen, Hao-Jing; Wang, Wei-Qiang; Lu, Zhizhou; Zhang, Wen-Fu; Guo, Guang-Can; Zou, Chang-Ling; Dong, Chun-Hua
  Source: OPTICS LETTERS  Volume: 49  Issue: 3  DOI: 10.1364/OL.511339  Published: 2024  
  Abstract:Recently, there has been significant interest in the generation of coherent temporal solitons in optical microresonators. In this Letter, we present a demonstration of dissipative Kerr soliton generation in a microrod resonator using an addition, we are able to control the repetition rate of the soliton over a range of 200 kHz while maintaining the pump laser frequency, by applying external stress tuning. Through the precise control of the PZT voltage, we achieve a stability level of 3.9 x 10(-10) for residual fluctuation of the repetition rate when averaged 1 s. Our platform offers precise tuning and locking capabilities for the repetition frequency of coherent mode-locked combs in microresonators. This advancement holds great potential for applications in spectroscopy and precision measurements. (c) 2024 Optica Publishing Group
  Accession Number:
  ISSN: 0146-9592
  eISSN: 1539-4794
• Record 137 of
  
  Title:Atom-referenced and stabilized soliton microcomb
  
  Author(s):Niu, Rui; Wan, Shuai; Hua, Tian-Peng; Wang, Wei-Qiang; Wang, Zheng-Yu; Li, Jin; Wang, Zhu-Bo; Li, Ming; Shen, Zhen; Sun, Yu Robert; Hu, Shui-Ming; Little, Brent E.; Chu, Sai Tak; Zhao, Wei; Guo, Guang-Can; Zou, Chang-Ling; Xiao, Yun-Feng; Zhang, Wen-Fu; Dong, Chun-Hua
  Source: SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY  Volume: 67  Issue: 2  DOI: 10.1007/s11433-023-2234-6  Published: 2024  
  Abstract:For the applications of the frequency comb in microresonators, it is essential to obtain a fully frequency-stabilized microcomb laser source. In this study, we present a system for generating a fully atom-referenced stabilized soliton microcomb. The pump light around 1560.48 nm is locked to an ultra-low-expansion (ULE) cavity. This pump light is then frequency-doubled and referenced to the atomic transition of 87Rb. The repetition rate of the soliton microcomb is injection-locked to an atomic-clock-stabilized radio frequency (RF) source, leading to mHz stabilization at 1 s. As a result, all comb lines have been frequency-stabilized based on the atomic reference and the ULE cavity, achieving a very high precision of approximately 18 Hz at 1 s, corresponding to the frequency stability of 9.5 x 10-14. Our approach provides a fully stabilized microcomb experiment scheme with no requirement of f-2f technique, which could be easily implemented and generalized to various photonic platforms, thus paving the way towards the ultraprecise optical sources for high precision spectroscopy.
  Accession Number: 224262
  ISSN: 1674-7348
  eISSN: 1869-1927
• Record 138 of
  
  Title:Wavefront Reconstruction Using Two-Frame Random Interferometry Based on Swin-Unet
  
  Author(s):Shu, Xindong; Li, Baopeng; Ma, Zhen
  Source: PHOTONICS  Volume: 11  Issue: 2  DOI: 10.3390/photonics11020122  Published: 2024  
  Abstract:Due to its high precision, phase-shifting interferometry (PSI) is a commonly used optical component detection method in interferometers. However, traditional PSI, which is susceptible to environmental factors, is costly, with piezoelectric ceramic transducer (PZT) being a major contributor to the high cost of interferometers. In contrast, two-frame random interferometry does not require precise multiple phase shifts, which only needs one random phase shift, reducing control costs and time requirements, as well as mitigating the impact of environmental factors (mechanical vibrations and air turbulence) when acquiring multiple interferograms. A novel method for wavefront reconstruction using two-frame random interferometry based on Swin-Unet is proposed. Besides, improvements have been made on the basis of the established algorithm to develop a new wavefront reconstruction method named Phase U-Net plus (PUN+). According to training the Swin-Unet and PUN+ with a large amount of simulated data generated by physical models, both of the methods accurately compute the wrapped phase from two frames of interferograms with an unknown phase step (except for multiples of pi). The superior performance of both methods is effectively showcased by reconstructing phases from both simulated and real interferograms, in comprehensive comparisons with several classical algorithms. The proposed Swin-Unet outperforms PUN+ in reconstructing the wrapped phase and unwrapped phase.
  Accession Number: 122
  ISSN:
  eISSN: 2304-6732
• Record 139 of
  
  Title:Enhanced Up-Conversion Emission of NaGdF4: Yb3+/Eu3+ Crystal via Li+ Doping for Anti-Counterfeiting Application
  
  Author(s):Wang Chong; Ren Zhong-xuan; Li Dong-dong; She Jiang-bo
  Source: SPECTROSCOPY AND SPECTRAL ANALYSIS  Volume: 44  Issue: 2  DOI: 10.3964/j.issn.1000-0593(2024)02-0497-07  Published: 2024  
  Abstract:Rare earth luminescent materials have gradually become a research hotspot in fluorescence anti-counterfeiting because of their high purity of luminous color, long fluorescent life, stable physical-chemical properties, and low toxicity. A series of NaGdF4:Yb3+/Eu3+ microcrystals co-doped with various Li+ concentrations were synthesized by the hydrothermal method in this paper. The samples' morphology, size, and up-conversion luminescence properties were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), up-conversion emission spectroscopy, and fluorescence lifetime tests. The crystal with strong luminous intensity was further applied to anti-counterfeiting identification. It shows that all the diffraction peaks of NaGdF4:Yb3+/Eu3+/Li+ microcrystals are consistent with the standard-NaGdF4 card. No impurity peak was found in the XRD pattern. The hexagonal NaGdF4:Yb3+/Eu3+/Li+ with high purity and crystallinity was synthesized. The SEM image of the crystal shows that the generated sample is a pure hexagonal phase, with uniform distribution, and no reunion. Co-doped Yb3+/Eu3+/Li+ has little effect on crystal structure, morphology and size. It can be seen from the up-conversion emission spectrum that the green luminescence intensity of 15 mol% Li+ doped NaGdF4:Yb3+/Eu3+ crystal is 6 times higher than that of the undoped Li+ sample. Adjust the power range of the laser to 0.8 similar to 2.2 W and observe the change in UCL intensity of the samples doped with 0 mol% Li+ and 15 mol% Li+. It can be observed that with the increase of pump power, the up-conversion intensity gradually increases. The number of photons required to generate the up-conversion luminescence n is close to 2, indicating that the emission process of the sample is a two-photon process. The fluorescence lifetime of the D-5(1) level in the sample is about 1.4 times that of the undoped one. Finally, the NaGdF4 : 0.2Yb/0.02Eu/0.15Li crystal with uniform morphology and strong luminous intensity was further applied as fluorescent ink. Screen printing technology printed The fluorescent anti-counterfeiting patterns on paper, glass and plastic. The pattern emitted bright green light under the pumping of a 980 nm laser. In the natural environment, the anti-counterfeiting pattern on the paper has good concealment. The word safe lenght is 5.5 mm, and the spacing between letters is 0.5 mm. The boundaries between letters are clear and easy to distinguish under 980 nm excitation. The plastic printed with the anti-counterfeiting pattern was exposed to the outdoor natural environment for a month, and the pattern did not change significantly. It shows that the anti-counterfeiting pattern made of NaGdF4 : 0.2Yb/0.02Eu/0.15Li has a high resolution, is easy to identify, and is less affected by the environment, and has excellent application prospects in anti-counterfeiting identification.
  Accession Number:
  ISSN: 1000-0593
  eISSN:
• Record 140 of
  
  Title:Methodology and Modeling of UAV Push-Broom Hyperspectral BRDF Observation Considering Illumination Correction
  
  Author(s):Wang, Zhuo; Li, Haiwei; Wang, Shuang; Song, Liyao; Chen, Junyu
  Source: REMOTE SENSING  Volume: 16  Issue: 3  DOI: 10.3390/rs16030543  Published: 2024  
  Abstract:The Bidirectional Reflectance Distribution Function (BRDF) is a critical spatial distribution parameter in the quantitative research of remote sensing and has a wide range of applications in radiometric correction, elemental inversion, and surface feature estimation. As a new means of BRDF modeling, UAV push-broom hyperspectral imaging is limited by the push-broom imaging method, and the multi-angle information is often difficult to obtain. In addition, the random variation of solar illumination during UAV low-altitude flight makes the irradiance between different push-broom hyperspectral rows and different airstrips inconsistent, which significantly affects the radiometric consistency of BRDF modeling and results in the difficulty of accurately portraying the three-dimensional spatial reflectance distribution in the UAV model. These problems largely impede the application of outdoor BRDF. Based on this, this paper proposes a fast multi-angle information acquisition scheme with a high-accuracy BRDF modeling method considering illumination variations, which mainly involves a lightweight system for BRDF acquisition and three improved BRDF models considering illumination corrections. We adopt multi-rectangular nested flight paths for multi-gray level targets, use multi-mode equipment to acquire spatial illumination changes and multi-angle reflectivity information in real-time, and introduce the illumination correction factor K through data coupling to improve the kernel, Hapke, and RPV models, and, overall, the accuracy of the improved model is increased by 20.83%, 11.11%, and 31.48%, respectively. The results show that our proposed method can acquire multi-angle information quickly and accurately using push-broom hyperspectral imaging, and the improved model eliminates the negative effect of illumination on BRDF modeling. This work is vital for expanding the multi-angle information acquisition pathway and high-efficiency and high-precision outdoor BRDF modeling.
  Accession Number: 543
  ISSN:
  eISSN: 2072-4292
• Record 141 of
  
  Title:Coherence analysis of supercontinuum generation in nitrobenzene liquid-core photonic crystal fiber based on adaptive step-size methods
  
  Author(s):Wen, Jin; Liang, Bozhi; Sun, Wei; He, Chenyao; Xiong, Keyu; Yu, Huimin; Zhang, Hui; Wu, Zhengwei; Wang, Qian
  Source: OPTICAL AND QUANTUM ELECTRONICS  Volume: 56  Issue: 4  DOI: 10.1007/s11082-023-06267-6  Published: 2024  
  Abstract:Methods for solving the generalized nonlinear Schrodinger equation (GNLSE) with adaptive step-size methods including the local error method (LEM) and conservation quantity error method (CQEM) are described. Supercontinuum generation (SCG) in liquid-core photonic crystal fibers (PCF) is numerically simulated by using LEM and CQEM in the time domain and frequency domain (FD) respectively. According to the numerical simulation results, the advantages and disadvantages of different adaptive step-size methods are compared, and the influence of different adaptive step-size methods on the coherence of SC is analyzed. A supercontinuum (SC) spectrum spanning from approximately 1300-2800 nm with high-coherence properties is numerically generated in the 5 cm fiber with 50 fs and 1000 W pump pulses at 1.55 mu m. The numerical results demonstrate that the performance of the SC generated in FD is also better because the nonlinear operator is more effective in FD. In addition, the pulse evolution process based on LEM is smoother and the coherence is better due to its higher number of iterations and accuracy, so it is adapted to accurately modeling the SCG in PCF. However, the CQEM is more computationally efficient and can minimize the computational effort, so it is suitable for the fast modeling of SCG in PCF. This numerical study helps to optimize the numerical process of SCG and find a new way for the generation of highly coherent SC.
  Accession Number: 619
  ISSN: 0306-8919
  eISSN: 1572-817X
• Record 142 of
  
  Title:Fourier Ptychographic Microscopy 10 Years on: A Review
  
  Author(s):Xu, Fannuo; Wu, Zipei; Tan, Chao; Liao, Yizheng; Wang, Zhiping; Chen, Keru; Pan, An
  Source: CELLS  Volume: 13  Issue: 4  DOI: 10.3390/cells13040324  Published: 2024  
  Abstract:Fourier ptychographic microscopy (FPM) emerged as a prominent imaging technique in 2013, attracting significant interest due to its remarkable features such as precise phase retrieval, expansive field of view (FOV), and superior resolution. Over the past decade, FPM has become an essential tool in microscopy, with applications in metrology, scientific research, biomedicine, and inspection. This achievement arises from its ability to effectively address the persistent challenge of achieving a trade-off between FOV and resolution in imaging systems. It has a wide range of applications, including label-free imaging, drug screening, and digital pathology. In this comprehensive review, we present a concise overview of the fundamental principles of FPM and compare it with similar imaging techniques. In addition, we present a study on achieving colorization of restored photographs and enhancing the speed of FPM. Subsequently, we showcase several FPM applications utilizing the previously described technologies, with a specific focus on digital pathology, drug screening, and three-dimensional imaging. We thoroughly examine the benefits and challenges associated with integrating deep learning and FPM. To summarize, we express our own viewpoints on the technological progress of FPM and explore prospective avenues for its future developments.
  Accession Number: 324
  ISSN:
  eISSN: 2073-4409
• Record 143 of
  
  Title:Design of Optical System for Ultra-Large Range Line-Sweep Spectral Confocal Displacement Sensor
  
  Author(s):Yang, Weiguang; Du, Jian; Qi, Meijie; Yan, Jiayue; Cheng, Mohan; Zhang, Zhoufeng
  Source: SENSORS  Volume: 24  Issue: 3  DOI: 10.3390/s24030723  Published: 2024  
  Abstract:The spectrum confocal displacement sensor is an innovative type of photoelectric sensor. The non-contact advantages of this method include the capacity to obtain highly accurate measurements without inflicting any harm as well as the ability to determine the object's surface contour recovery by reconstructing the measurement data. Consequently, it has been widely used in the field of three-dimensional topographic measuring. The spectral confocal displacement sensor consists of a light source, a dispersive objective, and an imaging spectrometer. The scanning mode can be categorized into point scanning and line scanning. Point scanning is inherently present when the scanning efficiency is low, resulting in a slower measurement speed. Further improvements are necessary in the research on the line-scanning type. It is crucial to expand the measurement range of existing studies to overcome the limitations encountered during the detection process. The objective of this study is to overcome the constraints of the existing line-swept spectral confocal displacement sensor's limited measuring range and lack of theoretical foundation for the entire system. This is accomplished by suggesting an appropriate approach for creating the optical design of the dispersive objective lens in the line-swept spectral confocal displacement sensor. Additionally, prism-grating beam splitting is employed to simulate and analyze the imaging spectrometer's back end. The combination of a prism and a grating eliminates the spectral line bending that occurs in the imaging spectrometer. The results indicate that a complete optical pathway for the line-scanning spectral confocal displacement sensor has been built, achieving an axial resolution of 0.8 mu m, a scanning line length of 24 mm, and a dispersion range of 3.9 mm. This sensor significantly expands the range of measurements and fills a previously unaddressed gap in the field of analyzing the current stage of line-scanning spectral confocal displacement sensors. This is a groundbreaking achievement for both the sensor itself and the field it operates in. The line-scanning spectral confocal displacement sensor's design addresses a previously unmet need in systematic analysis by successfully obtaining a wide measuring range. This provides systematic theoretical backing for the advancement of the sensor, which has potential applications in the industrial detection of various ranges and complicated objects.
  Accession Number: 723
  ISSN:
  eISSN: 1424-8220
• Record 144 of
  
  Title:Sub-Bin Delayed High-Range Accuracy Photon-Counting 3D Imaging
  
  Author(s):Yin, Hao-Meng; Zhao, Hui; Yang, Ming-Yang; Liu, Yong-An; Sheng, Li-Zhi; Fan, Xue-Wu
  Source: PHOTONICS  Volume: 11  Issue: 2  DOI: 10.3390/photonics11020181  Published: 2024  
  Abstract:The range accuracy of single-photon-array three-dimensional (3D) imaging systems is limited by the time resolution of the array detectors. We introduce a method for achieving super-resolution in 3D imaging through sub-bin delayed scanning acquisition and fusion. Its central concept involves the generation of multiple sub-bin difference histograms through sub-bin shifting. Then, these coarse time-resolution histograms are fused with multiplied averages to produce finely time-resolved detailed histograms. Finally, the arrival times of the reflected photons with sub-bin resolution are extracted from the resulting fused high-time-resolution count distribution. Compared with the sub-delayed with the fusion method added, the proposed method performs better in reducing the broadening error caused by coarsened discrete sampling and background noise error. The effectiveness of the proposed method is examined at different target distances, pulse widths, and sub-bin scales. The simulation analytical results indicate that small-scale sub-bin delays contribute to superior reconstruction outcomes for the proposed method. Specifically, implementing a sub-bin temporal resolution delay of a factor of 0.1 for a 100 ps echo pulse width substantially reduces the system ranging error by three orders of magnitude. Furthermore, Monte Carlo simulations allow to describe a low signal-to-background noise ratio (0.05) characterised by sparsely reflected photons. The proposed method demonstrates a commendable capability to simultaneously achieve wide-ranging super-resolution and denoising. This is evidenced by the detailed depth distribution information and substantial reduction of 95.60% in the mean absolute error of the reconstruction results, confirming the effectiveness of the proposed method in noisy scenarios.
  Accession Number: 181
  ISSN:
  eISSN: 2304-6732