湍流环境中水下成像系统的调制传递函数研究

Research of Modulation Transfer Function of Underwater Imaging System in Turbulent Environment

为了研究湍流对水下成像系统的影响,搭建了一套光学成像实验系统,利用水泵和水槽制造流速可控的湍流实验区域,使用CCD对正弦条纹目标成像,并分析图像质量。通过对实验环境的控制,得到不同浑浊度和不同流速下的成像结果,并提取调制传递函数(MTF)对结果进行分析。结果表明,悬浮颗粒散射在整个空间频率上造成调制对比度下降;而湍流散射更容易造成高空间频率域的MTF下降;随着进水口处流速的增加以及水体衰减系数的增大,其MTF曲线加快衰减;在湍流环境下的成像,图像失真和分辨率下降由颗粒散射和湍流散射共同造成。

In order to study the effect of turbulence on submarine imaging system,an optical experiment system is built using pump and tank to make the turbulence area with controllable water flow velocity.The CCD is used to imaging the sinusoidal fringe and the image quality is analyzed.The imaging results with various water turbidity and flow velocity are obtained through the control of imaging experiment environment.The modulation transfer function（MTF）is extracted to analyze the results.Experimental results show that the particle scattering causes modulation contrast declines in the whole spatial frequency.The effect caused by turbulence scattering is more obvious on the high frequency.With the increase of inlet flow velocity and the attenuation coefficient,the MTF curves show quick downward trends.The image distortion and decline of resolution are caused by the particle and turbulence scattering in the turbulent environment.