The extraction of polarization features is the key to the further application of remote sensors. For conventional remote sensing, the evaluation method of polarization characteristics is polarization sensitivity, which needs to be obtained through polarization testing. For polarization remote sensing, it is necessary to obtain the polarization characteristics of the instrument through polarization calibration. Polarization correction requires not only the measurement of the polarization characteristics of the target, but also the calibration of the polarization characteristics of the instrument, and the ultimate goal is to eliminate the polarization response of the instrument. Therefore, it is necessary to carry out research on polarization feature extraction and correction technology. This paper mainly discusses the difficulties and technical approaches of current polarization feature extraction and correction, analyzes the key technologies and related progress, and provides important reference value for further improving the quantitative acquisition of target information.
The polarization characteristic of ocean or atmospheric optical sensor is one of the important factors affecting the accuracy of radiation measurement and quantitative inversion. Based on the theory of polarization aberration, the physical mechanism of polarization sensitivity is analyzed in this paper, and the relationship between polarization aberration and polarization sensitivity is revealed. Moreover, a method of calculating the polarization sensitivity based on the Muller matrix is proposed. The computational analysis model is established based on the polarization ray tracing algorithm. This method overcomes the shortcomings of the traditional single ray estimation method and definition method, and the accuracy and efficiency of calculation are greatly improved. Take a remote camera as an example, the polarization sensitivity is analyzed theoretically and experimental measurement. This method can be applied to the imaging optical system or the imaging spectrometer for polarization analysis.
With the development of optical remote sensing technology, remote sensing constellation has attracted more and more attention because of its high time resolution. At present, countries all over the world are actively deploying remote sensing constellation, which has certainly become a research hotspot in the field of space remote sensing in China. The rapid development of remote sensing constellation also puts forward higher requirements for the quality and efficiency of space optical camera installation and adjustment, requiring high quality, short cycle and high precision. The traditional remote sensing camera installation and commissioning is mainly based on research and development and trial production mode. The assembly, debugging and fastening process of the system need to be iterated repeatedly, the development cycle is long, the index consistency is poor, and it is difficult to meet the large-scale development needs of remote sensing constellation construction. In order to solve this problem, this paper propose intelligent manufacturing and puts forward the intelligent assembly and detection technology. Firstly, the overall structure of the intelligent assembly detection technology is introduced, and the relevant process of the implementation of the intelligent detection technology is discussed. Then the key technical problems are analyzed, and the corresponding countermeasures are put forward. Finally, combined with the characteristics of intelligent assembly and detection technology, the process is decomposed. And independent testing unit is established, to realize the application of intelligent assembly and detection technology, which provides an important reference for the development of remote sensing constellation.
The grating spectrometer has high polarization sensitivity due to the existence of grating and other dispersive elements, which will directly affect the quantitative data acquisition accuracy of the instrument. Therefore, it is necessary to establish the polarization factor calculation model and measurement method of the grating spectrometer, and then quantitatively describe the polarization effect of the instrument.. The analysis method of quantitative polarization error is founded in this paper, and the polarization measurement device of incident light at discrete wavelength is proposed, in order to achieve the monitor of quantitative polarization error of hyper-spectral detector at central-wavelength. Finally, the quantitative polarization error is analyzed in radiation calibration, and the in-flight polarization error is predicted based on the polarization of incident light measured by SCIMACHY.
To realize the fast, high-quality alignment of off-axis reflective system, a computer-aided alignment method based on high-precision extraction of optical axis and high- precision restoration of surface shape of off-axis mirror was proposed. The optical axes of the mirrors are derived by means of a zero-position compensation detection path of the off-axis mirrors, and accuracy is better than 6", realize more rapid and accurate system initial alignment. There propose a surface shape data conversion algorithm, combined with Code V, it can realize the high-precision restoration of measured surface shape data of off-axis mirror in simulation, accurately calculate and separate the influence of shape error and position misalignment on system quality, and realize the fast and high precision alignment of off-axis reflective system. This method is applied to the practical alignment of one off-axis TMA system, wave aberration RMS≤0.084λ(λ=632.8nm) after initial alignment of the system. After only once calculation and alignment, full field RMS≤0.055λ. The experiment results demonstrate that this method is feasible.
The polarization characteristic of ocean or atmospheric optical sensor is one of the important factors affecting the accuracy of radiation measurement and quantitative inversion. According to polarization ray tracing algorithm, a calculating model of the polarization sensitivity based on the Muller pupil is proposed. A complete coastal zone remote sensor with low polarization sensitivity is designed, optimized and controlled, by the cooperative design of optical configuration compensating and coating. The result shows that the linear polarization sensitivity is less than 2.5% at B1, and below 1.5% for other four bands respectively.
The unification and recognition of meteorological parameter is the key to achieve long-time scale climate monitor, which is solved by space radiation benchmark with high precision. A space-borne whiskbroom solar reflection spectrum radiation benchmark is proposed in this paper, and the standard value transmission is more simple and reliable, achieved by the pendulum sweep institution with high stability. Based on the pendulum sweep institution, the spectral response of transfer and sun spectral radiometer and hyper-spectral earth imager is calibrated in-flight. And the primary benchmark is space-borne cryogenic absolute radiometer, whose absolute measurement uncertainty is 0.02%. Besides, the absolute measurement uncertainty of transfer and sun spectral radiometer and hyper-spectral earth imager is analyzed respectively in this paper, and the absolute measurement uncertainty is 0.23% and 0.63%.
The polarization sensitivity is an important factor of quantification of remote sensing information, which is used to evaluate polarization response of remote sensors. In this paper, the white light laser, polarizing film, and the beam expander system make up the polarization measurement system. And then the polarization test is accomplished. Unlike the traditional analysis, this paper proposed a method of Fourier series fitting to analyze the polarization test data. Compared with the cosine function fit, Fourier series fitting is closer to the real data, and the influence of natural light and elliptic polarized light. And it has advantage in the error analysis of polarization test and can help improve polarization test precision. At last, the errors of polarization measurement is analyzed.
A modified spectrometer with tandem gratings that exhibits high spectral resolution and imaging quality for solar observation, monitoring, and understanding of coastal ocean processes is presented in this study. Spectral broadband anastigmatic imaging condition, spectral resolution, and initial optical structure are obtained based on geometric aberration theory. Compared with conventional tandem gratings spectrometers, this modified design permits flexibility in selecting gratings. A detailed discussion of the optical design and optical performance of an ultraviolet spectrometer with tandem gratings is also included to explain the advantage of oblique incidence for spectral broadband.
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