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Proceedings Paper

Nonuniformly illuminated image enhancement based on range-gated underwater imaging system
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Paper Abstract

Range-gated underwater laser imaging technique can eliminate most of the backscattering and absorption noise effectively. It has a range of from 4 to 6 times that of a conventional camera with floodlights in the strongly scattering waters, which becomes a useful technique in oceanic research, deep-sea exploration, underwater remote control and robotic works. While because of the laser pulse stretching, the image obtained through range gated underwater imaging system has obvious nonuniformly illuminated character, such as brighter center and darker edge. Low contrast and grayish white of the image also bring great difficulty for processing. In order to adjust the lightness of the nonuniformly illuminated image of range-gated underwater imaging system, the water degradation is assumed as illumination variation and retinal-cortex theory based on color constancy is introduced. Frame integral algorithm has to be applied first to eliminate system noise for the reason that we adopt the system based on intensified gate imaging technology. And gray stretch ensures that we can attain appropriate output. In retinal-cortex models, McCann model and McCann-Frankle model have obvious effect. So we choose the two models for comparison and improve the second one considering the exponential characteristics of eyes for illumination. In order to evaluate the methods objectively, strength uniformity of signals is applied. The experimental results demonstrate that the approaches we adopted are all effective and can enhance the image contrast. And the improved McCann-Frankle model gets more satisfying visual effect.

Paper Details

Date Published: 28 January 2009
PDF: 8 pages
Proc. SPIE 7156, 2008 International Conference on Optical Instruments and Technology: Optical Systems and Optoelectronic Instruments, 71563E (28 January 2009); doi: 10.1117/12.812026
Show Author Affiliations
Hailan Li, Beijing Institute of Technology (China)
Xia Wang, Beijing Institute of Technology (China)
Tingzhu Bai, Beijing Institute of Technology (China)
Weiqi Jin, Beijing Institute of Technology (China)
Youwei Huang, Beijing Institute of Technology (China)
Kun Ding, Beijing Institute of Technology (China)

Published in SPIE Proceedings Vol. 7156:
2008 International Conference on Optical Instruments and Technology: Optical Systems and Optoelectronic Instruments
Yunlong Sheng; Yongtian Wang; Lijiang Zeng, Editor(s)

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