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Sheared-beam imaging technique is considered to be a non-conventional speckle technique for remote imaging through turbulent medium. In this high resolution imaging technique, three beams are splitted from one laser source and illuminate a remote target simultaneously in shearing distribution. Each beam is modulated by a tiny frequency shift so that these beams can interfere and beat together. The returning speckle signals are received by an array of detectors. The primary algorithm for the signal processing and image reconstruction has been developed previously. However, the reconstructed image is deteriorated by the frequency drifting error and spectrum leakage. These frequency errors are always from the transmitter and scattered signals that are caused by spectrum-shift errors from acoustic-optic modulators, atmospheric turbulence, Doppler effects of moving targets, etc. To solve the problems mentioned above, in this paper we propose a new image reconstruction algorithm based on the all-phase spectrum analysis theory. The all-phase fast Fourier transform (FFT) spectrum analysis theory, which can effectively inhibit spectral leakage and correct speckle spectrum, is used to process the scattered signals. By searching for the accurate positions of the beat frequency components in the transformed frequency domain data, the speckle amplitude and phase difference frames can be extracted accurately. Based on the speckle phase-difference frames, the phase distribution of the wavefront is derived by least-square algorithm. The phase distribution in grid is highly coherent, in which each point is related to the phases of its four nearest neighbors. If an initial phase map is given or preset, the phase map of the wavefront can be estimated accurately by Gauss-Seidel method. Meanwhile, the amplitude of wavefront is obtained by the algebraic operation of speckle amplitude frames. The reconstructed wavefront is inverse Fourier transformed to yield a two dimensional image. A series of speckled images of the same object are averaged to reduce the speckle noise. The proposed method improves the ability of system imaging in the actual imaging environment. Simulation experiments validate the effectiveness of the proposed algorithm, and simulation results show that the proposed image reconstruction algorithm can inhibit the frequency errors from influencing imaging quality when there exist frequency errors in scattered signals. Thus, the imaging quality of the algorithm based on the all-phase FFT method is much better than that of the algorithm based on the traditional FFT method. The substantial usage of this technique is widely spread after the reconstruction algorithm has been optimized.
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Keywords:
- sheared-beam imaging /
- speckle /
- all-phase spectrum analysis /
- target reconstruction
[1] Hutchin R A US Patent 20120162631[2012-6-28]
[2] Hutchin R A US Patent 20120292481[2012-11-22]
[3] Voelz D G 1996 Proc. SPIE 2566 74
[4] Voelz D G, Belsher J F, Ulibarri A L, Gamiz V 2002 Proc. SPIE 4489 35
[5] Hutchin R A 1993 Proc. SPIE 2029 161
[6] Voelz D G, Gonglewski J D, Idell P S 1993 Proc. SPIE 2029 169
[7] Stahl S M, Kremer R, Fairchild P, Hughes K, Spivey B 1996 Proc. SPIE 2847 150
[8] Olson D F, Long S M, Ulibarri L J 2000 Proc. SPIE 4091 323
[9] Huang X D 2006 Ph. D. Dissertation (Tianjin:Tianjin University) (in Chinese)[黄翔东2006博士学位论文(天津:天津大学)]
[10] Huang X D, Wang Z H 2008 J. Electron. & Inform. Technol. 30 293 (in Chinese)[黄翔东, 王兆华2008电子与信息学报30 293]
[11] Huang X D, Wang Z H 2007 J. Tianjin University 40 883 (in Chinese)[黄翔东, 王兆华2007天津大学学报40 883]
[12] Cao B, Luo X J, Chen M L, Zhang Y 2015 Acta Phys. Sin. 64 124205 (in Chinese)[曹蓓, 罗秀娟, 陈明徕, 张羽2015 64 124205]
[13] Chen W, Li Q, Wang Y G 2010 Acta Opt. Sin. 30 3441 (in Chinese)[陈卫, 黎全, 王雁桂2010光学学报30 3441]
[14] Landesman B T, Olson D F 1994 Proc. SPIE 2302 14
[15] Bush K A, Barnard C C, Voelz D G 1996 Proc. SPIE 2828 362
[16] Goodman J W 1985 Statistical Optics (New York:John Wiley) p495
[17] Zebker H A, Lu Y 1998 J. Opt. Soc. Am. A 15 586
[18] Idell P S, Gonglewski J D 1990 Opt. Lett. 15 1309
[19] Cao B, Luo X J, Si Q D, Zeng Z H 2015 Acta Phys. Sin. 64 054204 (in Chinese)[曹蓓, 罗秀娟, 司庆丹, 曾志红2015 64 054204]
[20] Zhang W X, Xiang L B, Kong X X, Li Y, Wu Z, Zhou Z S 2013 Acta Phys. Sin. 62 164203 (in Chinese)[张文喜, 相里斌, 孔新新, 李扬, 伍洲, 周志盛2013 62 164203]
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[1] Hutchin R A US Patent 20120162631[2012-6-28]
[2] Hutchin R A US Patent 20120292481[2012-11-22]
[3] Voelz D G 1996 Proc. SPIE 2566 74
[4] Voelz D G, Belsher J F, Ulibarri A L, Gamiz V 2002 Proc. SPIE 4489 35
[5] Hutchin R A 1993 Proc. SPIE 2029 161
[6] Voelz D G, Gonglewski J D, Idell P S 1993 Proc. SPIE 2029 169
[7] Stahl S M, Kremer R, Fairchild P, Hughes K, Spivey B 1996 Proc. SPIE 2847 150
[8] Olson D F, Long S M, Ulibarri L J 2000 Proc. SPIE 4091 323
[9] Huang X D 2006 Ph. D. Dissertation (Tianjin:Tianjin University) (in Chinese)[黄翔东2006博士学位论文(天津:天津大学)]
[10] Huang X D, Wang Z H 2008 J. Electron. & Inform. Technol. 30 293 (in Chinese)[黄翔东, 王兆华2008电子与信息学报30 293]
[11] Huang X D, Wang Z H 2007 J. Tianjin University 40 883 (in Chinese)[黄翔东, 王兆华2007天津大学学报40 883]
[12] Cao B, Luo X J, Chen M L, Zhang Y 2015 Acta Phys. Sin. 64 124205 (in Chinese)[曹蓓, 罗秀娟, 陈明徕, 张羽2015 64 124205]
[13] Chen W, Li Q, Wang Y G 2010 Acta Opt. Sin. 30 3441 (in Chinese)[陈卫, 黎全, 王雁桂2010光学学报30 3441]
[14] Landesman B T, Olson D F 1994 Proc. SPIE 2302 14
[15] Bush K A, Barnard C C, Voelz D G 1996 Proc. SPIE 2828 362
[16] Goodman J W 1985 Statistical Optics (New York:John Wiley) p495
[17] Zebker H A, Lu Y 1998 J. Opt. Soc. Am. A 15 586
[18] Idell P S, Gonglewski J D 1990 Opt. Lett. 15 1309
[19] Cao B, Luo X J, Si Q D, Zeng Z H 2015 Acta Phys. Sin. 64 054204 (in Chinese)[曹蓓, 罗秀娟, 司庆丹, 曾志红2015 64 054204]
[20] Zhang W X, Xiang L B, Kong X X, Li Y, Wu Z, Zhou Z S 2013 Acta Phys. Sin. 62 164203 (in Chinese)[张文喜, 相里斌, 孔新新, 李扬, 伍洲, 周志盛2013 62 164203]
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