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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Accurate and Traceable Determination of Raman Shifts in Reference Material by Continuous-Wave Stimulated Raman Spectroscopy
摘要： Most Raman spectrometers require frequent calibration in order to provide accurate and repeatable results, and the calibration interval decreases for operation at high resolution. Wavenumber calibration commonly uses emission lines from gas-discharge lamps (e.g. mercury, neon, argon) that provide well-defined frequencies with very low uncertainties. However, it is often impractical to align lamps properly at the sample position, and the lamp emission lines provide absolute frequencies rather than Raman shifts. A more practical alternative is the use of a reference sample with a known Raman spectrum, which allows for the calibration of Raman spectrometer regardless of the excitation wavelength. Polystyrene is commonly used as a reference as it is easily available and practical to handle. We report on the application of continuous-wave stimulated Raman spectroscopy (CW-SRS) for accurate measurement of Raman shifts in polystyrene samples. Due to the narrow linewidth of CW radiation, CW-SRS achieves spectral resolution that is several orders of magnitude below those obtained with common Raman spectrometer or pulsed-based SRS. Furthermore, CW-SRS enables direct determination of the Raman shift by measuring the difference of pump and probe frequencies. For our application, we used an 852 nm diode laser as probe and a widely tunable external cavity diode laser as pump covering the wavelength range from 781 nm to 787 nm. Stimulated Raman gain was measured by modulating the pump amplitude at 10.4 MHz and detecting scattered light on the probe with a balanced photodetector and spectrum analyser. High frequency modulation and balanced detection ensured shot noise limited operation, which was confirmed by the scaling of the noise level and signal with probe power up to 4.5 mW (Fig. 1 (b)). Polystyrene spectra in the range 968 cm-1 to 1059 cm-1 were recorded by scanning the pump wavelength. Both pump and probe wavelengths were measured accurately by a wavelength meter traceable to a frequency standard. Values and uncertainties of the Raman shift of two Raman transitions in polystyrene were calculated according to the Guide to the Expression of Uncertainty in Measurement (GUM) [1]. The method was applied to two different polystyrene samples: a thin plate taken from a tool cabinet and a NIST traceable reference sample for FTIR. For the later, Raman shifts of 1001.15 ± 0.04 cm-1 and 1031.33 ± 0.21 cm-1 were measured. Compared with existing standards [2], we achieve up to one order of magnitude improvement on the uncertainty of the measured Raman shifts, thereby improving the metrology capability for characterization of reference material for Raman spectroscopy. Furthermore, shot noise operation paves the way towards the development of quantum-enhanced SRS with potential application in biological imaging.
关键词： Raman spectroscopy,continuous-wave stimulated Raman spectroscopy,metrology,polystyrene,calibration
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Enhancement of QEPAS Sensitivity Based-on Quartz Resonance Frequency Tracking
摘要： This study reports on the development of a platform based-on a Field-Programmable Gate Arrays (FPGAs) and suitable for high speed measurements and enhancement of QEPAS sensitivity.
关键词： Algorithm,Spectroscopy,Calibration
更新于2025-09-12 10:27:22
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Accuracy and biases in predicting the chemical and physical traits of many types of cheeses using different visible and near-infrared spectroscopic techniques and spectrum intervals
摘要： Near-infrared spectroscopy (NIRS) has been widely used to determine various composition traits of many dairy products in the industry. In the last few years, near-infrared (NIR) instruments have become more and more accessible, and now, portable devices can be easily used in the field, allowing the direct measurement of important quality traits. However, the comparison of the predictive performances of different NIR instruments is not simple, and the literature is lacking. These instruments may use different wavelength intervals and calibration procedures, making it difficult to establish whether differences are due to the spectral interval, the chemometric approach, or the instrument’s technology. Hence, the aims of this study were (1) to evaluate the prediction accuracy of chemical contents (5 traits), pH, texture (2 traits), and color (5 traits) of 37 categories of cheese; (2) to compare 3 instruments [2 benchtop, working in reflectance (R) and transmittance (T) mode (NIRS-R and NIRS-T, respectively) and 1 portable device (VisNIRS-R)], using their entire spectral ranges (1100–2498, 850–1048, and 350–1830 nm, respectively, for NIRS-R, NIRS-T and VisNIRS-R); (3) to examine different wavelength intervals of the spectrum within instrument, comparing also the common intervals among the 3 instruments; and (4) to determine the presence of bias in predicted traits for specific cheese categories. A Bayesian approach was used to develop 8 calibration models for each of 13 traits. This study confirmed that NIR spectroscopy can be used to predict the chemical composition of a large number of different cheeses, whereas pH and texture traits were poorly predicted. Color showed variable predictability, according to the trait considered, the instrument used, and, within instrument, according to the wavelength intervals. The predictive performance of the VisNIRS-R portable device was generally better than the 2 laboratory NIRS instruments, whether with the entire spectrum or selected intervals. The VisNIRS-R was found suitable for analyzing chemical composition in real time, without the need for sample uptake and processing. Our results also indicated that instrument technology is much more important than the NIR spectral range for accurate prediction equations, but the visible range is useful when predicting color traits, other than lightness. Specifically for certain categories (i.e., caprine, moldy, and fresh cheeses), dedicated calibrations seem to be needed to obtain unbiased and more accurate results.
关键词： chemometric,texture trait,cheese quality,water-soluble protein,Bayesian calibration
更新于2025-09-12 10:27:22
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[IEEE IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium - Yokohama, Japan (2019.7.28-2019.8.2)] IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium - A Rigorous on-orbit Geometric Calibration Method for High-Resolution Optical Sensor of Chinese Mapping Satellite
摘要： Internationally, the technology of optical earth observation satellite is developing in the direction of miniaturization, high-resolution and high maneuverability. High-precision on-orbit geometric calibration of the imaging sensors is the most important guarantee of interior geometric quality and direct positioning accuracy of the satellite images. The high-resolution camera of Chinese Mapping Satellite-1 is a multi-chip TDICCD optical sensor in triangular mechanical staggered stitching structure. To improve the accuracy and robustness of its geometric calibration while reducing the correlation between calibration parameters, this paper proposed a new multi-chip pointing angle model for internal calibration and an optimized imaging model for external calibration. The overlapping connection relation between multi-chip TDICCDs of an image and multi-scene images are fully utilized for constructing the calibration error equations with constraints. Then, the internal and external calibration are iteratively solved through relaxation block adjustment method. Experimental results demonstrate that the proposed rigorous on-orbit geometric calibration method can effectively and stably eliminate various system errors of the imaging system, thus improving the interior and exterior geometric quality of image production.
关键词： high-resolution satellite image,TDICCD optical sensor,quality evaluation,Geometric calibration
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE International Conference on Mechatronics and Automation (ICMA) - Tianjin, China (2019.8.4-2019.8.7)] 2019 IEEE International Conference on Mechatronics and Automation (ICMA) - Research on 3D Reconstruction Method Based on Laser Rotation Scanning
摘要： A three-dimensional reconstruction algorithm based on line laser rotation scanning is proposed. The rotating platform vision measurement system is designed. The system calibration method consisting of laser, camera and turntable is studied. The axis-eye calibration algorithm is introduced to register the point cloud in the same coordinate. In the system, the camera driven by the turntable is rotated to scan the target object for three-dimensional measurement. The method can obtain the point cloud information of the object by linear laser rotation scanning, and further recover the geometric shape of the three-dimensional visible surface of the object, which not only meets the requirements of the three-dimensional reconstruction target, but also verifies the feasibility and effectiveness of the system.
关键词： rotating platform,camera calibration,feature point extraction,point cloud reconstruction,3d reconstruction
更新于2025-09-12 10:27:22
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A Calibration Method for the Errors of Ring Laser Gyro in Rate-Biased Mode
摘要： Ring laser gyro (RLG) can work in mechanically dithered mode or rate-biased mode according to the working state of the inertial navigation system (INS). It can change from one mode to the other by receiving outer instructions. To evaluate the performance of RLG in rate-biased mode, an inertial measurement unit (IMU) based on RLG is installed on a dual-axis turntable, the turntable offers a constant angular velocity to the RLGs, in that way RLG can work in the rate-biased mode. A calibration method is proposed to calibrate the scale factor error, misalignments and constant bias of RLG in rate-biased mode, experiment results show that the differences of scale factor of the three gyros in two modes are 9 ppm, 7 ppm and 3.5 ppm, the constant biases of the three RLGs in rate-biased mode are also different from that in mechanically dithered mode with the difference of 0.017°/h, 0.011°/h and 0.020°/h, the input axis misalignment angle of RLGs in different modes also changed. What is more, a calculation method of angle random walk (ARW) of RLG in rate-biased mode is also presented. Experimental results show that the ARW of the RLG in rate-biased mode is about one third of that in mechanically dithered.
关键词： ring laser gyroscopes,angle random walk,gyroscopes,calibration
更新于2025-09-12 10:27:22
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Laser Scanning Confocal Image Alignment Assists Sub-micron Accuracy Micro-assembly
摘要： The image resolution of the ordinary optical microscope in the assembly system can’t break through the optical diffraction limit, and the accuracy of alignment detection can’t reach the sub-micron level. So we build the micro assembly system based on the principle of confocal image alignment to solve the above problems. In this paper, the basic principle and system of confocal image alignment assembly are studied, and the levelling calibration method of the platform is also studied. After the calibration, the alignment resolution of the micro assembly system based on the principle of confocal image alignment can reach 0.5μm.The confocal image alignment principle is verified by the assembly application experiment of inserting a 125-μm-diameter optical fiber into a 127-μm-diameterglass micro tubule. The confocal image alignment principle and the calibration method can greatly improve the accuracy and efficiency of the micro assembly.
关键词： Precision microassembly,Submicron precision,Confocal alignment,Levelling calibration
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE International Conference on Mechatronics and Automation (ICMA) - Tianjin, China (2019.8.4-2019.8.7)] 2019 IEEE International Conference on Mechatronics and Automation (ICMA) - Kinematics Calibration of Spraying Robot based on Laser Tracker
摘要： A method for industrial spraying robot calibration by using laser tracker is presented in this paper. Firstly, the structure of spraying robot is analysed and the coordinate systems of each joint are configured based on D-H method; Secondly, the kinematics model of spraying robot is established, and the error model of the spraying robot is established based on the differential transformation. Thus the functional equation between the position error of the end-effector and the D-H parameters is obtained; Thirdly, laser tracker is used to measure the actual position of the end-effector, and the error of D-H parameters of each joint are iteratively solved based on the kinematics error model; Finally, the error value is compensated to the robot motion control model for verification. The results of the experiment show that the absolute precision of the robot is improved greatly after calibration.
关键词： Kinematics Calibration,Laser Tracker,Spraying robot,Kinematics modeling
更新于2025-09-12 10:27:22
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Iterative Pointing Angle Calibration Method for the Spaceborne Photon-Counting Laser Altimeter Based on Small-Range Terrain Matching
摘要： The satellite, Ice, Cloud and Land Elevation Satellite-2 (ICESat-2) has been equipped with a new type of spaceborne laser altimeter, which has the benefits of having small footprints and a high repetition rate, and it can produce dense footprints on the ground. Focusing on the pointing angle calibration of this new spaceborne laser altimeter, this paper proposes a fast pointing angle calibration method using only a small range of terrain surveyed by airborne lidar. Based on the matching criterion of least elevation difference, an iterative pointing angle calibration method was proposed. In the experiment, the simulated photon-counting laser altimeter data and the Ice, Cloud and Land Elevation Satellite-2 data were used to verify the algorithm. The results show that when 1 km and 2.5 km lengths of track were used, the pointing angle error after calibration could be reduced to about 0.3 arc-seconds and less than 0.1 arc-seconds, respectively. Meanwhile, compared with the traditional pyramid search method, the proposed iterative pointing angle calibration method does not require well-designed parameters, which are important in the pyramid search method to balance calculation time and calibration result, and the iterative pointing angle calibration method could significantly reduce the calibration time to only about one-fifth of that of the pyramid search method.
关键词： ICESat-2,photon-counting,pointing angle calibration,spaceborne laser altimeter,terrain matching
更新于2025-09-12 10:27:22
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Phase Difference Measurement of Under-Sampled Sinusoidal Signals for InSAR System Phase Error Calibration
摘要： Phase di?erence measurement of sinusoidal signals can be used for phase error calibration of the spaceborne single-pass interferometric synthetic aperture radar (InSAR) system. However, there are currently very few papers devoted to the discussion of phase di?erence measurement of high-frequency internal calibration signals of the InSAR system, especially the discussion of sampling frequency selection and the corresponding measuring method when the high-frequency signals are sampled under the under-sampling condition. To solve this problem, a phase di?erence measurement method for high-frequency sinusoidal signals is proposed, and the corresponding sampling frequency selection criteria under the under-sampling condition is determined. First, according to the selection criteria, the appropriate under-sampling frequency was chosen to sample the two sinusoidal signals with the same frequency. Then, the sampled signals were ?ltered by limited recursive average ?ltering (LRAF) and coherently accumulated in the cycle of the baseband signal. Third, the ?ltered and accumulated signals were used to calculate the phase di?erence of the two sinusoidal signals using the discrete Fourier transform (DFT), digital correlation (DC), and Hilbert transform (HT)-based methods. Lastly, the measurement accuracy of the three methods were compared respectively by di?erent simulation experiments. Theoretical analysis and experiments veri?ed the e?ectiveness of the proposed method for the phase error calibration of the InSAR system.
关键词： interferometric synthetic aperture radar (InSAR),under-sampling,phase di?erence measurement,coherent accumulation,phase error calibration
更新于2025-09-12 10:27:22