反向追迹法获取水下对空全景图像

Obtaining water-to-air panoramic images by inverse ray tracing method

  • 摘要: 在水下透过波浪对海面及空中目标成像,所获取的目标图像会发生畸变。为定量分析波浪对图像畸变的影响,建立一种理想的水下对空成像模型,得到透过波浪的全景图像。首先,在给定的成像模型下,运用主光线反向追迹法,由斯涅耳定律计算出与水下入射光线对应的水上折射光线的方向矢量,从而得到天球上目标点与成像靶面上单像素点的物像对应关系。然后,对整个成像靶面上的像素点进行遍历,形成水下对空全景图像。最后,在4种特殊的海面波浪波形下,利用MATLAB环境计算出天空圆形目标及背景的水下对空全景图像。计算结果表明:运用反向追迹法能够有效地计算出水下对空全景图像,通过调整波浪参数,可以定量分析图像的畸变程度。主光线反向追迹法适用于分析透过具有一阶可导波浪的水下对空全景图像的畸变特征,为研究更复杂波浪下的水下对空图像畸变特征奠定了基础。

     

    Abstract: The water-to-air images of sea surface and air targets through wavy surface will be distorted. In order to quantitatively analyze the effect of sea surface waveform on image distortion, an ideal water-to-air imaging model was established so as to obtain the panoramic image through the waveform. Firstly, based on the given imaging model, the main-ray inverse tracing method was used to calculate the direction vector of overwater refracted ray corresponding to the underwater incident ray by Snell’s law, and the corresponding relation of objective image between the target point on the celestial sphere and the single pixel point on the imaging target surface was obtained. Then, all the pixel points on the imaging target surface were traversed, and a water-to-air panoramic image was formed. Finally, based on the four kinds of special waveform, the water-to-air panoramic image of sky circular target and background was calculated in MATLAB environment. The calculation results show that the water-to-air panoramic image can be effectively calculated by the inverse ray tracing method and can be quantitatively analyzed the image distortion degree by adjusting the waveform parameters. The main-ray inverse tracing method is suitable for analyzing the distortion characteristics of the water-to-air panoramic image with first-order guided waves, which lays a foundation for studying the distortion characteristics of water-to-air image under more complex waves.

     

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