Effects of antenna array configurations on imaging quality in Fourier telescopy
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Cited by 2 publications
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Improving coherent field imaging quality by suppressing the influence of transmitting aperture spacing error
Coherent field imaging is based on the assumption of equal transmitting apertures spacing and equal spectrum of laser, and high-resolution image is reconstructed by iteratively computing the frequency spectrum. However, the inevitable transmitting aperture spacing error of laser is a key factor to affect the coherent field imaging quality in the application. Aiming at the problem of degrading imaging quality caused by the transmitting aperture spacing error, we discuss the mechanism of influence of aperture spacing error on imaging quality and propose a novel method of improving imaging quality from the perspective of suppressing the influence of transmitting aperture spacing error. Firstly, the mechanism of the influence of aperture spacing error on imaging quality and laser echo spectrum is analyzed in detail. Then we derive a frequency spectrum error propagation model. Based on the model, the iterative effect of frequency spectrum error is investigated and the trend of variation in imaging quality with frequency spectrum error is given. We propose a theoretical equation, in which the transmitting aperture spacing error has no influence on frequency spectrum nor imaging quality. To solve the above equation, an optimized method of linear programming is proposed and the optimized matrix of aperture spacing error is obtained. In practice, the influence of aperture spacing error on imaging quality can be largely counteracted by reasonably allocating aperture spacing error according to the optimized spacing error matrix. The correctness and validity of the theoretical model are verified by a simulation experiment. The results show that the Strehl ratio of imaging quality index can be improved by about 100% through using the proposed method, the greater the aperture spacing error, the higher the Strehl ratio of imaging quality index obtained by the method will be. In addition, the method is easy to use practically and less costly as well. Finally, it is concluded that the proposed method can easily and effectively counteract the degrading effect of aperture spacing error on imaging quality. The research can provide a theoretical basis for improving imaging quality and reasonably assigning transmitter aperture spacing accuracy of coherent field imaging telescope.
Improving coherent field imaging quality by suppressing the influence of transmitting aperture spacing error
Coherent field imaging is based on the assumption of equal transmitting apertures spacing and equal spectrum of laser, and high-resolution image is reconstructed by iteratively computing the frequency spectrum. However, the inevitable transmitting aperture spacing error of laser is a key factor to affect the coherent field imaging quality in the application. Aiming at the problem of degrading imaging quality caused by the transmitting aperture spacing error, we discuss the mechanism of influence of aperture spacing error on imaging quality and propose a novel method of improving imaging quality from the perspective of suppressing the influence of transmitting aperture spacing error. Firstly, the mechanism of the influence of aperture spacing error on imaging quality and laser echo spectrum is analyzed in detail. Then we derive a frequency spectrum error propagation model. Based on the model, the iterative effect of frequency spectrum error is investigated and the trend of variation in imaging quality with frequency spectrum error is given. We propose a theoretical equation, in which the transmitting aperture spacing error has no influence on frequency spectrum nor imaging quality. To solve the above equation, an optimized method of linear programming is proposed and the optimized matrix of aperture spacing error is obtained. In practice, the influence of aperture spacing error on imaging quality can be largely counteracted by reasonably allocating aperture spacing error according to the optimized spacing error matrix. The correctness and validity of the theoretical model are verified by a simulation experiment. The results show that the Strehl ratio of imaging quality index can be improved by about 100% through using the proposed method, the greater the aperture spacing error, the higher the Strehl ratio of imaging quality index obtained by the method will be. In addition, the method is easy to use practically and less costly as well. Finally, it is concluded that the proposed method can easily and effectively counteract the degrading effect of aperture spacing error on imaging quality. The research can provide a theoretical basis for improving imaging quality and reasonably assigning transmitter aperture spacing accuracy of coherent field imaging telescope.
Theoretical research of influence of laser intensity fluctuation on imaging quality degradation of coherent field
The laser coherent field imaging system emits multiple beams of laser from earth to space, and laser scans remote space target by passing through turbulence atmosphere. Multi-beam laser intensity fluctuation caused by atmosphere turbulence is a key factor affecting high-resolution imaging quality of the coherent field imaging system. Aiming at solving the problem of imaging quality degradation caused by laser intensity fluctuation error, we discuss the mechanism of laser intensity fluctuation error influencing the imaging quality of laser coherent field high-resolution imaging system. The theoretical model about the relationship between laser intensity fluctuation factor and imaging quality is proposed for the first time. Firstly, the laser echo field signal error induced by laser intensity amplitude fluctuation factor is deduced according to laser transmitting atmosphere theory. Then adopting multi-beam phase closure arithmetic, the phase closure coefficient error is derived from the laser intensity fluctuation factor and laser echo field signal. The mechanism of disturbed laser echo signal influencing phase closure coefficient is investigated in detail. In the following, based on reconstructed spectrum theory, the model of imaging frequency spectrum error propagation, caused by laser intensity fluctuation factor, is proposed. Finally, we reveal the mechanism of laser intensity amplitude fluctuation factor influencing reconstructed imaging frequency spectrum and imaging quality. The correctness and validity of the theoretical model are verified in simulation experiment. In the three-beam laser coherent field imaging simulation experiment, the imaging quality is evaluated by the Strehl ratio of the image. Experimental result shows that the Strehl ratio is only related to the light intensity fluctuation of one of the three beams of laser, and the greater the fluctuation of laser intensity, the more serious the degradation of imaging quality is. The research draws the conclusion that the reconstructed imaging frequency spectrum and image quality are mainly affected by the laser intensity fluctuation of the second beam in the three-beam phase closure algorithm, regardless of other two laser intensity fluctuations. Thus, in order to restrain the degradation of imaging quality caused by laser intensity fluctuation, we only need to keep stable the laser intensity of the second beam but not all of the laser beams. In this paper, we reveal the mechanism of laser intensity fluctuation affecting high-resolution imaging quality in the three-beam laser coherent field imaging system. The research provides a theoretical basis for analyzing imaging quality degradation from the laser intensity fluctuation caused by atmospheric turbulence, and reasonably assigning the light intensity stability of multi-beam laser emitter to improve the imaging quality in laser coherent field imaging system.
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