Study On The Restraint Method And Characteristics Of Background Interference For Self-guidance Of Light Wakes

In this paper the restraint method and characteristics of background interference for self-guidance of light wakes which based on the laser illumination to detect the air bubbles in the ship wake is studied. The theoretical and experimental investigation shown that the valid ways how to restrain the background interference are as following. Set up a narrowband optical spectrum filter to a photoelectric detector with transmission coefficient just cover the spectrum of illuminating laser radiation. The scattering interference of water molecules and solid suspended particles can be restrained effectually by the 0°(forward) scattering measurement. Measure the scattered light's spatial spectrum intensity distribution of air bubbles in water, through Gaussian Fitting, using the Full Width at Half Maximum (FWHM) of scattered light's spatial spectrum intensity distribution to token the air bubbles'spatial distribution, this is an effectually method for ship wake detecting, what is more, it can restraint the interference of sunlight whose spectrum is coincidence with that of laser radiation. Wavelet Noise-reduction is adopted to reduce the noise induced by photoelectric detector during the process of photoelectric conversion, so that the Gaussian Fitting curve what has been processed by wavelet noise-reduction is more approximately to the practical detected spatial spectrum distribution of bubbles scattering. Afterward, the real-time detecting system for ship wake bubbles'scattered light was designed and completed. The system adopts the four-level pipeline structure, which consists of the CCD optical signal acquisition section, analog-to-digital converter (A/D) data acquisition section, DSP processing section and USB output data section.