Study and implementation for range-gated underwater laser imaging system

The report provides the principle and advances of range-gated Underwater Laser Imaging Technology. A prototype Underwater Laser Imaging System has been designed and developed. The range-gated technique is one of the effective methods to decrease the backward scattering of the water media. This report provides the study and implementation for range-gated Underwater Laser Imaging System (ULIS). A careful analysis of the novel Underwater Laser Imaging System (ULIS) shows that a range-gated system will have a significantly improved viewing performance over conventional systems. The system uses a 2-kHz diode-pumped frequency doubled Nd:YAG laser as an illumination source. The light is collected by a 5-cm-diam zoom lens. The detector is a gated image CCD detector with a 10-ns gate. In the strongly scattering waters, this system has a range of from three to five times that of a conventional camera with floodlights. By the use of the lower attenuation window for the water media in the visible light spectrum, pulse laser with the blue-green wavelength has been adopted as an illumination source and CCD as the receiver. The range-gated underwater laser imaging system has been successfully fulfilled. The system can decrease the influence of backward scattering and at the same time the system can improve target luminance. The detail schematic principle and realization scheme have been analyzed. It has been found that the range-gated underwater laser imaging system could improve the imaging quality and the imaging distance by conveniently adjusting the pulse delay and the pulse width. It has been become one of the key techniques in underwater laser imaging research field.