Research Of Underwater Imaging Detection Technology In Inhomogeneous Illumination Field

Underwater imaging detection takes on an importance role in military and civil ocean exploitation and technical application. One of the key problems in underwater imaging detection is to overcome backward scattering effect. A new underwater image detection theory, inhomogeneous illumination field theory, is proposed to reduce the backward scattered background noise and increase both imaging quality and observed space.In inhomogeneous illumination field, the three-dimensional distribution of underwater illumination field follows the principle of light attenuation in the water. When object is close to visual reception systems, lower density energy is used to illuminate the target in order to reduce the backward scattering noise influence as far as possible. When object is far away to visual reception systems, higher density energy is used to illuminate it in order to increase target signal's intensity, at the same time overcome target signal's scattering noise and receiver's background noise.The implementation method of inhomogeneous illumination field is given out in the thesis. An underwater image detection system with distributive light with central power source is constructed. The distribution function of inhomogeneous illumination field is derived. It relates to receive aperture, distance between target and receiver as well as seawater volume attenuation coefficient. When other parameters are definite, the illumination field intensity is required stronger when the distance between target and receiver is increasing. It basically follows exponent law between illumination field intensity and observe instance.The visibility of inhomogeneous illumination field is researched in the thesis. As same as the visibility theory of homogeneous illumination field, the visibility of inhomogeneous illumination field depends on contrast instead of receiver's sensitivity and illumination intensity. The visibility model of inhomogeneous illumination field is given out. A conclusion is drawn:The visibility of inhomogeneous illumination field is mainly influenced by scatter volume coefficientΔl.The relation between visibility and scatter volume coefficient, receiver's visual angel, optical axis distance also is researched in the thesis.In order to offer theory foundation to design of distributive light with central power source, the source's illumination function and distribution function are researched in the thesis. The change principle of source's illumination function is deduced.The character of source's distribution function is analyzed. A conclusion is drawn:In any kinds of water, the source's energy will increase 10 times when the attenuation length increases one times.An underwater image detection system with distributive light of central power, includes underwater probing part, above-water control part and connected cable,is developed to verification the theory of inhomogeneous illumination field. The tank contrast experiment is proposed, which verifies the inhomogeneous illumination field's distribution characteristic and underwater probing characteristic. The experimental result proven:The underwater image detection system based on inhomogeneous illumination field theory has wide visual angle, far detection distance and good image definition properties.The technology of inhomogeneous illumination field can overcome the influence of underwater backward scattering noise. It would multiply the underwater detect space greatly. The underwater observation technology based on this theory will not only promote the underwater observation theories, but also can be applicated in observation of aerospace and war vessel in atrocious weather.