Remote Sensing and Sensors|19 Article(s)
Optimization for Closed-Loop Surface Plasmon Resonance Fiber-Optic Refractive Index Sensors Based on Tapered Probes
FU Li-hui, YIN Wen-qing, WANG Ma-hua, JI Ren-dong, and JU Yong-feng
For the sake of optimizing its measure range,sensetivity and linearity, a tapered Surface Plasmon Resonance (SPR) fiber probe was applied as the substitution of the uniform fiber probe because of its abundant lossy modes.Simulation results and experimental data shew that this tapered probe had a SPR asorption spectrum with better symmetry and its resonance wavelength could change responsing to a bigger range of measured refractive index with a stable wavelength resolution. After constructing a closed-loop SPR fiber sensors based on the tapered probe according to frequency modulation principle, the deionized water sucrose and ethanol solution, whose refractive index value ranged from 1.33 RI unit (RIU)to 1.43 RIU with different concentration, were elected as measurand.The measured results were analyzed and verfied using an Abel refractive index meter.The experimental results demonstrated that the closed-loop SPR fiber-optic sensors with a tapered SPR probe had the sensitivity of 0.00003 RIU, wavelength resolution of 4500 nm/RIU and with better performance in terms of dynamic range, sensetivity and linearity, than that with a uniform SPR probes.
Acta Photonica Sinica
  • Publication Date: Feb. 01, 2015
  • Vol. 44 Issue 2 228001 (2015)
Fast Azimuth Imaging Algorithm of Inverse Synthetic Aperture Ladar for Maneuvering Targets
WANG Hong-yan, RUAN Hang, and WU Yan-hong
The Doppler frequency time-variation exist in the received echo when imaging maneuvering targets by Inverse Synthetic Aperture Laser radar (ISAL). Based on a keystone transform in the azimuth time-frequency domain, a fast azimuth imaging algorithm of ISAL for maneuvering targets is proposed. Since the ratio of the chirp rate to the initial frequency is constant for all multicomponent linear frequency modulation subechoes in each range cell, all these multicomponent linear frequency modulation subechoes can be simultaneously transformed into multi-component single frequency subechoes by using the keystone transform in the azimuth time-frequency domain, and hence fast Fourier transform can be used for azimuth focusing. In addition, a precise and efficient method based on the fractional Fourier transform and the minimum entropy is proposed to estimate the ratio of the chirp rate to the initial frequency. Simulation results prove that, comparing with the range-instantaneous Doppler algorithm based on the Radon-Wigner transform, the proposed algorithm is more efficient and can preserve more information details of the target.
Acta Photonica Sinica
  • Publication Date: Feb. 01, 2015
  • Vol. 44 Issue 2 228002 (2015)
Methane Concentration Monitoring System Based on Connecting Move Type Anti-jamming Interferometer Underground
LIU Zhi-chao, and YANG Jin-hua
To effectively monitor methane concentration in the underground, for interference large characteristics underground , combined with real-time monitoring for methane concentration requirements, self-eliminate vibration optical structure was designed with rectangular prism linked, and the real-time data communication system was constructed based on the wireless network. In interferometer system, the position of two rectangular prism were fixed. The two beam splitters with connecting rod so that it can rotate synchronously, and the optical path difference is generated by rotation. As a result of the link structure, the vibration introduced into the two beam splitters are present in equal amounts at any time. Because the results was calculated used the difference value, therefore, it can be completely destructive effect. By analyzing the maximum range of rotation of beam splitter, the optical path difference range of the system can be calculated. Then through Beer-Lambert law, methane gas concentration detection limit of the system was given in the underground. Experiment in the laboratory and in the main mine roadway were completed, the measured standard concentration of methane gas obtained through a chemical reaction, and the results was compared to test results of WQF530 type spectrum analyzer. The results show that under the conditions of non-interference in the laboratory, the relative error of two detection methods were less than 1.0%;In the underground experiments, the test results of conventional optical detection methods significantly affected by the environment, and relative error was greatly increased, but the test results of the system was stable. So it is strong anti-interference ability and stability.
Acta Photonica Sinica
  • Publication Date: Feb. 01, 2015
  • Vol. 44 Issue 2 228003 (2015)
Super Resolution Optic Three-dimensional Imaging Based on Compressed Sensing
WANG Feng, LUO Jian-jun, TANG Xing-jia, LI Li-bo, and HU Bin-liang
A super resolution optic three-dimensional imaging based on compressed sensing was proposed for better optic imaging, in which imaging system was consisted of object glass, coding template, dispersion element, collimating lens, focus lens, detector in the front, hyperspectral data was reconstructed in the end by sparse reconstruction algorithm, so the most of data processing was transformed to the back-end from the imaging system. Meanwhile, Piece reconstruction, dislocation pretreatment and multi-frame reconstruction were used for improving accuracy of reconstruction, reducing memory of the back-processing, lowing computation complexity. By comparing the spectral curve, signal noise ratio, spectral error of the original and the reconstructed data cube, and doing classification and identification analysis, it was gained that the proposed compressed sensing could realize super resolution optic three-dimensional imaging, which have better property in imaging and data application, it can be used in big breath, high resolution, low power consumption and moving-target imaging observation.
Acta Photonica Sinica
  • Publication Date: Mar. 01, 2015
  • Vol. 44 Issue 3 328001 (2015)
Super Resolution ISAR Imaging in Receiver Centered Region Area in Bistatic Radar
ZHANG Long, SU Tao, LIU Zheng, HE Xiao-hui, and DUAN Yong-qiang
For the time-variant property of bistatic angles in Receiver Centered Region Area in bistatic radar system, it′s difficult to obtain high resolution ISAR image of target in by using the conventional imaging methods.The signal model for bistatic ISAR was presented, then the time-variant property of the bistatic angles and its influence on range envelope and azimuth was analyzed.A Radon-TCDS-Relax super-resolution imaging method was brought up for eliminate the effect from high-order azimuth terms of target motion model in receiver centered areas.The chirp rate and its changing rate corresponding to high-order phase terms in cross range was estimated by the proposed method.Scatterers extracting and imaging were achieved by Radon-TCDS-RELAX and TCD-RID respectively.Accuracy analysis and the experimental results with real data both demonstrate the effectiveness of the proposed method.
Acta Photonica Sinica
  • Publication Date: Mar. 01, 2015
  • Vol. 44 Issue 3 328002 (2015)
Analysis of Underlying Surface Impact on Non-synchronous Alternative Spectral Calibration
XU Ai-jun, YUAN Juan, ZHANG Wen-juan, CHEN Zheng-chao, ZHANG Ya-qiong, and LI Hai-wei
In order to provide calibration image selection strategy for non-synchronous alternative spectral calibration, the oxygen absorption band near 760 nm was studied, spectral data of five underlying surface types of vegetation, withered vegetation, manmade objects, sand and snow were chosen to analysize. Based on simulated data, the analysis of calibration results and the accuracy was carried out, and spectral calibration errors of different underlying surface types was compared. Results showed that calibration errors based on the spectral angle matching method and the euclidean distance method are almost the same. When standard deviations of surface reflectance are less than 0.05 nm in 730 nm-800 nm, the spectral calibration precision is within ±0.5 nm. The olive green gloss paint and lush vegetation are not suitable to non-synchronous alternative spectral calibration.
Acta Photonica Sinica
  • Publication Date: Mar. 01, 2015
  • Vol. 44 Issue 3 328003 (2015)
Humidity Sensor Based on Waist-enlarged Fiber Tapers Cascade Structure
ZHANG Yun-shan, QIAO Xue-guang, SHAO Min, FU Hai-wei, LI Hui-dong, and ZHAO Na
An in-fiber Mach-Zehnder interferometer humidity sensor based on waist-enlarged fiber tapers cascade structure was proposed and demonstrated.The sensor head is formed by a taper-single-mode-taper-single-mode-taper structure through arc fusion splicing.The change of the humidity and temperature will make the optical path difference changed of the sensor core mode and cladding modes, causing interference spectral change.Through monitoring the spectra variation can determine the ambient physical quantities.The experimental results show that the humidity sensitivity of the sensor is -0.065 dB/%RH with a linearity of 0.997 in the humidity range of 35-95%RH;the temperature sensitivity of the sensor is 69.4 pm/℃ with a linearity of 0.998 in the temperature range of 30-80 ℃.This sensor can avoid the cross-sensitivity to humidity and temperature, make it a good candidate for high accuracy humidity and temperature applications.
Acta Photonica Sinica
  • Publication Date: Mar. 01, 2015
  • Vol. 44 Issue 3 328004 (2015)
Space Target Luminosity Measurement Based on Video Remote Sensing Satellites
Yan MA, Chi MA, Yan-hao XIE, and Fang WANG
Experiments on measuring the photometric characteristics of space targets were conducted based on Jilin-1 video satellites, the method of using video satellite to image space targets and perform luminosity inversion were demonstrated. The inversion and estimation on luminosity characteristics of targets was based on grey scale value of output images from camera sensor. An analysis on the effect from the error of radiation calibration coefficient and image noise on the inversion precision was also conducted based on the principle of error transfer. By using star targets as the standard radiation source, the inversion precision was verified. Results show the error of luminosity inversion is less than 0.15 magnitude. A statistics analysis on targets filmed by Jilin-1 satellites was performed and examples were listed, giving estimation on the maximum sensing distance, probability of target capture and the observation performance. Results show that the agile imaging mode of video satellite which is designed for ground remote sensing performs well in space target observation as well.
Acta Photonica Sinica
  • Publication Date: Dec. 25, 2019
  • Vol. 48 Issue 12 1228002 (2019)
Advances and Prospects of Laser Measurement Technology for Air Motion Parameters(Invited)
Yazhou YUE, Bin LI, and Hongjie LEI
The air motion parameters (such as air speed, angle of attack, angle of sideslip, etc.) of an aircraft, which are important source parameters for flight control, navigation, and mission decision making, are usually measured by traditional airborne air data system, and can be used in flight stability control, accurate navigation and precise weapon launch. But the traditional air data system can no longer meet the performance requirements of modern military and civil aircraft in maneuverability, stealth, reliability, safety, comfort and economy due to the performance defects, such as measurement failure at low air speed and large maneuvers, significant aerodynamic delay, pitot tube icing, poor stealth performance, susceptibility to aircraft air turbulence, requiring complex compensation, etc., which result from its mechanical, nonlinear, near the fuselage measurement characteristics. To overcome the defects of the traditional air data system, the method using laser technology for measuring air motion parameters was first developed abroad, which can completely solve the defects of traditional airborne air data system due to its characteristics of high accuracy, high linearity, measurement far away form fuselage, embedded installation, etc..In this paper, the principle, characteristics, advantages and disadvantages of the traditional method and laser method for measuring air motion parameters are compared and analyzed. The obvious advantages and advancements of the laser measurement technology for air motion parameters make it a research hotspot at home and abroad. Throughout the technology development, the laser measurement technology for air motion parameters can be categorized two schemes including direct detection and coherent detection. The principle and composition of the two technical schemes are presented. Then the advantages and disadvantages of the two technical schemes are compared.The two technical schemes of laser measurement technology for air motion parameters, which have their advantages respectively, are developed synchronously nowadays and have been widely used. The application areas mainly include three aspects: accurate measurement of air motion parameters, flight calibration of conventional air data system and detection of wind shear and turbulence ahead of the aircraft. In this article, the development and application are mainly reviewed in these three aspects, and the achievements of prototype and flight test results in these three application aspects are provided. As can be seen from the research reports, the research institutes are mainly concentrated in Europe and America, including OADS corporation, Ophir corporation, Michigan Aerospace corporation, Thales corporation, ONERA, EADS, DLR, etc. Many flight tests have been carried out and a large number of test data have been accumulated by these institutes. At present, the prototype which can be equipped and applied has been successfully developed abroad. In contrast, domestic research is relatively backward, the main research institutions are AVIC CAIC and AVIC FACRI. In recent years, the principle prototype has been reported by the two research institutes respectively.The development direction of the two schemes of air motion parameters measurement technology are prospected respectively. The coherent detection scheme is likely to be first equipped for airborne application due to its low size, weight and power property. The detection capability of the coherent detection scheme at high altitude up to tens of kilometers needs to be continuously improved. The direct detection scheme should further reduce the size, weight, power and costs to meet the requirements of airborne applications. The application of quantum technology in laser measurement technology for air motion parameters is prospected. In the future, single photon detection technology and quantum enhancement technology based on compressed state photon are expected to be applied to improve the detective sensitivity of the system and achieve ultra-sensitive detection. In view of the huge development gap between home and abroad, some useful suggestions are provided for domestic research of laser measurement technology for air motion parameters, such as robust related industrial chain, focus on low SWaP performance design, strengthen cooperation, increase capital investment, etc.The purpose of review and further clarification of the principle, application and development trend of laser measurement technology for air motion parameters is to provide a useful reference and new ideas for the researchers engaged in prototype and application research, and to promote the in-depth application of laser measurement technology for air motion parameters in aviation fields.
Acta Photonica Sinica
  • Publication Date: Apr. 25, 2022
  • Vol. 51 Issue 4 0428001 (2022)
Optimization Algorithm for Polarization Remote Sensing Cloud Detection Based on Machine Learning
Jiejun WANG, Shaohui LIU, Shu LI, Song YE, Xinqiang WANG, and Fangyuan WANG
The polarization remote sensing experience threshold cloud detection algorithm is strongly affected by subjective factors, and it is very easy to have the problem of inaccurate cloud detection over bright ground. In response to this problem, this paper proposes a machine learning cloud detection algorithm that combines active and passive remote sensing satellites. The algorithm is based on the multi-channel multi-angle polarization characteristics of the POLDER3 payload and the high-precision cloud vertical characteristics of the CALIOP payload. It uses POLDER3 payload and CALIOP. The load observation overlaps the regional data, and the BP neural network optimized by the Particle Swarm Optimization algorithm is built to train the cloud detection model. Based on the cloud detection training model, a cloud detection experiment was carried out using POLDER3 level-1 data. The experiment showed that the cloud detection result of this algorithm is 92.46% consistent with the MODIS cloud detection product, which is higher than the consistency between the official POLDER3 cloud detection product and the MODIS cloud detection product 83.13%. By comparing the experimental results of the algorithm in this paper with the optical characteristics of different pixels from the official POLDER3 cloud detection product, it is found that compared with the official POLDER3 algorithm, this algorithm is more sensitive to thin clouds over the bright surface and can perform cloud detection more effectively.
Acta Photonica Sinica
  • Publication Date: Feb. 25, 2021
  • Vol. 50 Issue 2 166 (2021)