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Iterative Back Projection Reconstruction for Underwater Imaging
Y-Z. Chen, H-Y. Tan, W-L. Yang, Y. Yang, N. Hao and K-C. Yang

It is known that underwater image formation is affected not only by absorption and scattering properties of water, but also the optical systems including lenses and sensors. Applications such as image enhancement and restoration can effectively remove the blur and degradation, but the resolution is still limited. Image super-resolution reconstruction (SRR) techniques such as iterative back projection (IBP) method are promising approaches for improving resolution beyond the limit of hardware. With knowledge of the point spread function (PSF), the performance of the super-resolution reconstruction can be further enhanced, which will be beneficial to various underwater imaging or detecting applications. The presented effort applies several PSF models including a simplified model based on beam transmission considering time-related backscattering as well as an imagery-derived approach based on measurement to the IBP method for underwater range-gated imaging, blind and objective image quality metrics are used for evaluation, experimental results of which show adequate improvement and flexibility provided by the proposed approaches.

Keywords: Nd:YAG laser, iterative back projection (IBP), modulation transfer function (MTF), point spread function (PSF), super-resolution reconstruction (SRR)

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