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Image quality is seriously degraded when propagating through the turbid atmosphere. It is practical to characterize the degradation process in terms of modulation transfer function (MTF). The MTF can describe the effect of the turbid medium on imaging quantitatively in spatial frequency domain, including attenuation and multiple scattering. It is inherent property of the turbid medium. The whole spatial frequency characteristic of the turbid atmosphere MTF can be acquired through the equivalence principle, i, e., the equivalence between the MTF of a turbid medium and the transmitted radiance from the medium under isotropic diffuse illumination. In practice, the image quality is not only affected by the turbid medium MTF but also related tightly to the background radiation. The influence of scattered background radiation on imaging was almost not considered in the past when dealing with the imaging problem in the turbid atmosphere. In this paper, this issue is considered in detail. The analysis results demonstrate that the scattered background radiation increases the zero frequency component of image in spatial frequency domain. As a result, it degrades the image contrast seriously in spatial domain. Based on the optical model of image degradation in the atmosphere, the theoretical analysis is carried out to study the image quality degradation process in spatial frequency domain. The formalized MTF is proposed, which considers the effects of attenuation, multiple scattering and scattered background radiation by the turbid medium on image quality. The quantitative relation among the formalized MTF, turbid medium MTF and background radiation is confirmed. Image blur simulations show that the results from the formalized MTF are more consistent with actual scenes than results only from turbid medium MTF. Thus, the formalized MTF can describe the image degradation process through atmosphere comprehensively. The image restoration results indicate that the formalized MTF method performs better than dark channel prior method. In order to evaluate different image restoration methods effectively in spatial frequency domain, spectrum area (AS) is proposed. The AS is the area of middle-high frequency information of the region of interest in restored image. So AS can represent the scene details in the restored image. The higher the AS, the better the image quality is, which is demonstrated in this paper. In conclusion, the formalized MTF provides a more effective method for image quality analysis and assessment. Additionally, it also supplies a new standpoint for researching atmospheric degradation mechanism and correction method for imaging in turbid atmosphere. Then, AS can be an effective reference for correction to the method evaluation.
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Keywords:
- image quality analysis /
- turbid medium /
- modulation transfer function /
- background radiation
[1] Eismann M T 2012 Hyperspectral Remote Sensing (Washington:SPIE Press) pp1-81
[2] Wang Z, Alan C B 2006 Modern Image Quality Assessment (USA:Morgan Claypool Publishers) pp33-36
[3] Xiong X H 2004 Sci. Survey. Map. 29 1 (in Chinese)[熊兴华 2004 测绘科学 29 1]
[4] Rao R Z 2012 Modern Atmospheric Optics (Beijing:Science Press) pp514-543 (in Chinese)[饶瑞中 2012 现代大气光学 (北京:科学出版社) 第514543页]
[5] LeMaster D A, Esimann M T 2012 Proc. SPIE 8355 1
[6] Esimann M T, LeMaster D A 2013 Opt. Eng. 52 046201
[7] Lutomirski R F 1978 Appl. Opt. 17 3915
[8] Kopeika N S 1982 J. Opt. Soc. Am. 72 548
[9] Sadot D, Kopeika N S 1993 J. Opt. Soc. Am. A 10 172
[10] Wells W H 1969 J. Opt. Soc. Am. 59 686
[11] Kuga Y, Ishimaru A 1986 Appl. Opt. 25 4382
[12] Rao R Z 2012 Chin. Opt. Lett. 10 020101
[13] Wu P F 2013 Ph. D. Dissertation (Beijing:University of Chinese Academy of Sciences) (in Chinese)[武鹏飞 2013 博士学位论文(北京:中国科学院大学)]
[14] Henyey L G, Greenstein J L 1941 Astrophys. J. 93 70
[15] Narasimhan S G, Nayar S K 2003 IEEE Trans. PAMI 25 713
[16] Norman S K 1998 A System Engineering Approach to Imaging (Washington:SPIE Press) pp517-541
[17] Gerald C H (translated by Yan J X, Yu X, Xie T B, Yao H J) 2015 Electro-Optical Imaging System Performance (Fourth Edition)(Beijing:National Defense Industry Press) pp121-141 (in Chinese)[Gerald C H (阎吉祥, 俞信, 解天宝, 姚和军 译) 2015 光电成像系统性能(第四版)(北京:国防工业出版社)第121141页]
[18] He K M, Sun J, Tang X O 2009 IEEE Trans. PAMI 33 2341
[19] He K M, Sun J, Tang X O 2013 IEEE Trans. PAMI 35 1397
[20] Gonzalez R C, Woods R E 2002 Digital Image Processing (Second Edition)(New Jersey:Prentice Hall) pp261-265
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[1] Eismann M T 2012 Hyperspectral Remote Sensing (Washington:SPIE Press) pp1-81
[2] Wang Z, Alan C B 2006 Modern Image Quality Assessment (USA:Morgan Claypool Publishers) pp33-36
[3] Xiong X H 2004 Sci. Survey. Map. 29 1 (in Chinese)[熊兴华 2004 测绘科学 29 1]
[4] Rao R Z 2012 Modern Atmospheric Optics (Beijing:Science Press) pp514-543 (in Chinese)[饶瑞中 2012 现代大气光学 (北京:科学出版社) 第514543页]
[5] LeMaster D A, Esimann M T 2012 Proc. SPIE 8355 1
[6] Esimann M T, LeMaster D A 2013 Opt. Eng. 52 046201
[7] Lutomirski R F 1978 Appl. Opt. 17 3915
[8] Kopeika N S 1982 J. Opt. Soc. Am. 72 548
[9] Sadot D, Kopeika N S 1993 J. Opt. Soc. Am. A 10 172
[10] Wells W H 1969 J. Opt. Soc. Am. 59 686
[11] Kuga Y, Ishimaru A 1986 Appl. Opt. 25 4382
[12] Rao R Z 2012 Chin. Opt. Lett. 10 020101
[13] Wu P F 2013 Ph. D. Dissertation (Beijing:University of Chinese Academy of Sciences) (in Chinese)[武鹏飞 2013 博士学位论文(北京:中国科学院大学)]
[14] Henyey L G, Greenstein J L 1941 Astrophys. J. 93 70
[15] Narasimhan S G, Nayar S K 2003 IEEE Trans. PAMI 25 713
[16] Norman S K 1998 A System Engineering Approach to Imaging (Washington:SPIE Press) pp517-541
[17] Gerald C H (translated by Yan J X, Yu X, Xie T B, Yao H J) 2015 Electro-Optical Imaging System Performance (Fourth Edition)(Beijing:National Defense Industry Press) pp121-141 (in Chinese)[Gerald C H (阎吉祥, 俞信, 解天宝, 姚和军 译) 2015 光电成像系统性能(第四版)(北京:国防工业出版社)第121141页]
[18] He K M, Sun J, Tang X O 2009 IEEE Trans. PAMI 33 2341
[19] He K M, Sun J, Tang X O 2013 IEEE Trans. PAMI 35 1397
[20] Gonzalez R C, Woods R E 2002 Digital Image Processing (Second Edition)(New Jersey:Prentice Hall) pp261-265
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