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Sheared-beam imaging, which is a nonconventional coherent laser imaging technique, can be used to better solve the problem of taking pictures with high resolution for remote targets through turbulent medium than conventional optical methods. In the previous research on this technique, a target was illuminated by three coherent laser beams that were laterally arranged at the transmitter plane into an L pattern. In order to obtain a high quality image, a series of time-varying scattered signals is collected to reconstruct speckled images of the same object. To overcome atmospheric turbulence, multiple sets of three-beam laser should be emitted, which increases data acquisition time. In this paper, aiming at the quasi real-time problem of conventional sheared beam imaging technique, we use four-beam laser with rectangular distribution instead of the traditional L type sheared three-beam laser to illuminate the target. According to this, we propose a target reconstruction algorithm for four-beam sheared coherent imaging to reconstruct four target images simultaneously in one measurement, which can acquire high quality images by reducing the amount of measurement and the speckle noise. Meanwhile, it can greatly reduce the amount of beam switching in multi-group emission and improve the imaging efficiency. Firstly, the principle of the four-beam sheared coherent imaging technique is deduced. Secondly, in the algorithm, the speckle amplitude and phase difference frames can be extracted accurately by searching for the accurate positions of the beat frequency components. Based on the speckle phase difference frames, four sets of wavefront phases can be demodulated by the least squares method, and wavefront amplitude can be obtained by algebraic operation of speckle amplitude. The reconstructed wavefront is used for inverse Fourier transform to yield a two-dimensional image. A series of speckled images is averaged to form an incoherent image. Finally, the validity of the proposed technique is verified by simulations. From the simulation results, the image quality of the proposed method is better than that of the traditional method in the same amount of measurement. Furthermore, on the premise of the same image quality, the data acquisition amount of the proposed method is 2-3 times as large as that of the traditional method. In other words, compared with that of the traditional method, the data acquisition time of the proposed method is reduced at least by half and the algorithm processing time is less. It can be concluded that the proposed imaging technique can not only improve the efficiency of target reconstruction, but also present a better way of imaging the remote moving targets.
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Keywords:
- sheared coherent imaging /
- four-beam /
- target reconstruction /
- imaging efficiency
[1] Voelz D G 1995 Proc. SPIE 2566 74
[2] Voelz D G, Belsher J F, Ulibarri A L, Gamiz V 2002 Proc. SPIE 4489 35
[3] Rider D B, Voelz D G, Bush K A, Magee E 1993 Proc. SPIE 2029 150
[4] Hutchin R A 1993 Proc. SPIE 2029 161
[5] Voelz D G, Gonglewski J D, Idell P S 1993 Proc. SPIE 2029 169
[6] Sica L 1996 Appl. Opt. 35 264
[7] Bush K A, Barnard C C, Voelz D G 1996 Proc. SPIE 2828 362
[8] Olson D F, Long S M, Ulibarri L J 2000 Proc. SPIE 4091 323
[9] Gamiz V L 1994 Proc. SPIE 2302 2
[10] Hutchin R A US Patent 20120292481 [2012-11-22]
[11] Hutchin R A US Patent 20120162631 [2012-06-28]
[12] Landesman B T, Olson D F 1994 Proc. SPIE 2302 14
[13] Chen M L, Luo X J, Zhang Y, Lan F Y, Liu H, Cao B, Xia A L 2017 Acta Phys. Sin. 66 024203 (in Chinese) [陈明徕, 罗秀娟, 张羽, 兰富洋, 刘辉, 曹蓓, 夏爱利 2017 66 024203]
[14] Landesman B T, Kindilien P, Pierson R E 1997 Opt. Express 1 312
[15] Stahl S M, Kremer R, Fairchild P, Hughes K, Spivey B 1996 Proc. SPIE 2847 150
[16] Zebker H A, Lu Y P 1998 J. Opt. Soc. Am. A 15 586
[17] Takajo H, Takahashi T 1988 J. Opt. Soc. Am. A 5 1818
[18] Hudgin R H 1977 J. Opt. Soc. Am. A 67 375
[19] Idell P S, Gonglewski J D 1990 Opt. Lett. 15 1309
[20] 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]
[21] 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]
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[1] Voelz D G 1995 Proc. SPIE 2566 74
[2] Voelz D G, Belsher J F, Ulibarri A L, Gamiz V 2002 Proc. SPIE 4489 35
[3] Rider D B, Voelz D G, Bush K A, Magee E 1993 Proc. SPIE 2029 150
[4] Hutchin R A 1993 Proc. SPIE 2029 161
[5] Voelz D G, Gonglewski J D, Idell P S 1993 Proc. SPIE 2029 169
[6] Sica L 1996 Appl. Opt. 35 264
[7] Bush K A, Barnard C C, Voelz D G 1996 Proc. SPIE 2828 362
[8] Olson D F, Long S M, Ulibarri L J 2000 Proc. SPIE 4091 323
[9] Gamiz V L 1994 Proc. SPIE 2302 2
[10] Hutchin R A US Patent 20120292481 [2012-11-22]
[11] Hutchin R A US Patent 20120162631 [2012-06-28]
[12] Landesman B T, Olson D F 1994 Proc. SPIE 2302 14
[13] Chen M L, Luo X J, Zhang Y, Lan F Y, Liu H, Cao B, Xia A L 2017 Acta Phys. Sin. 66 024203 (in Chinese) [陈明徕, 罗秀娟, 张羽, 兰富洋, 刘辉, 曹蓓, 夏爱利 2017 66 024203]
[14] Landesman B T, Kindilien P, Pierson R E 1997 Opt. Express 1 312
[15] Stahl S M, Kremer R, Fairchild P, Hughes K, Spivey B 1996 Proc. SPIE 2847 150
[16] Zebker H A, Lu Y P 1998 J. Opt. Soc. Am. A 15 586
[17] Takajo H, Takahashi T 1988 J. Opt. Soc. Am. A 5 1818
[18] Hudgin R H 1977 J. Opt. Soc. Am. A 67 375
[19] Idell P S, Gonglewski J D 1990 Opt. Lett. 15 1309
[20] 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]
[21] 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]
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