Dr. Hongwei Han Profile

Dr. Hongwei Han

at Naval Univ of Engineering

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Publications (3)

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Proceedings Article | 5 January 2017 Paper

Influence of size of the spherical scatterers and the attenuation coefficient on the polarization memory based on the Electric Monte Carlo simulation

Feng Guan, Xiaohui Zhang, Hongwei Han, Wei Zhong

Proceedings Volume 10244, 1024419 (2017) https://doi.org/10.1117/12.2266755

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When light travels in water, the state of polarization of the incident light changes as the photons are scattered with suspended particles or reflected on the target surface. In order to increase the working distance, underwater polarized light imaging (UPLI) technology usually makes use of the different depolarization effect between the water body and target on the incident polarized light to filter the backscattered light. So it is significant to study the depolarization characteristics of polarized light in water. In this paper, a Field Monte Carlo (EMC) program is developed to simulate the transmission characteristics of polarized light in water with specific particle and attenuation coefficient. EMC method is different from the traditional Monte Carlo method which tracks the Stokes vector of the beam. It uses the Jones mechanism to characterize the polarization state of the photons. By tracking the two vertical components of the photonic vibrating electric vector, the polarization state and the depolarization effect of polarized light transmitted through a body of water can be obtained. The simulation results are based on horizontal polarization, vertical polarization, 45 degree linearly polarized light(LPL) and right circularly polarized light(CPL) as incident light , Stokes vectors of four types of received light is obtained respectively, and the related parameters are calculated to analyze the polarization memory performance. The numerical results show that water body have good polarization memory property and the influence of the particle size and the attenuation coefficient on the LPL is obvious than that circularly of the polarized light, and the CPL has better polarization memory ability.

Proceedings Article | 5 January 2017 Paper

Computational polarization difference underwater imaging based on image fusion

Hongwei Han, Xiaohui Zhang, Feng Guan

Proceedings Volume 10244, 102440U (2017) https://doi.org/10.1117/12.2264269

KEYWORDS: Polarization, Underwater imaging, Image fusion

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Polarization difference imaging can improve the quality of images acquired underwater, whether the background and veiling light are unpolarized or partial polarized. Computational polarization difference imaging technique which replaces the mechanical rotation of polarization analyzer and shortens the time spent to select the optimum orthogonal ǁ and ⊥axes is the improvement of the conventional PDI. But it originally gets the output image by setting the weight coefficient manually to an identical constant for all pixels. In this paper, a kind of algorithm is proposed to combine the Q and U parameters of the Stokes vector through pixel-level image fusion theory based on non-subsample contourlet transform. The experimental system built by the green LED array with polarizer to illuminate a piece of flat target merged in water and the CCD with polarization analyzer to obtain target image under different angle is used to verify the effect of the proposed algorithm. The results showed that the output processed by our algorithm could show more details of the flat target and had higher contrast compared to original computational polarization difference imaging.

Proceedings Article | 15 October 2015 Paper

The optical detection in turbid water by range-gated imaging system with HPRF laser

Liang-hong Hua, Hong-wei Han, Xiao-hui Zhang

Proceedings Volume 9674, 967408 (2015) https://doi.org/10.1117/12.2196923

KEYWORDS: Imaging systems, Pulsed laser operation, Signal to noise ratio, Image quality, Image intensifiers, Image filtering, Charge-coupled devices, Sensors, Image processing, Photons

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In the field of underwater sensing, the rang-gated imaging based on the principle of “time slice” is an effective way to suppress backscatter and improve operating distance. In this paper, a kind of underwater range-gated imaging system which selects the LD end-pumped solid laser as the illuminator is described. Comparing to the traditional ones using the lamp-pumped Nd: YAG laser, the prime characteristics of the new designed underwater range-gated imaging system lie in the dramatic dropping of single pulse energy and the dramatic increasing of pulse repetition frequency, and the resultant change of echo receiving pattern throughout the image formation. The advantage and disadvantage of the change is first analysed in this paper, and then the underwater range-gated imaging system with high pulse repetition frequency (HPRF) laser is introduced. Finally, the experiment results in the indoor tank and the corresponding analysis is provided.

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