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分析了激光主动成像图像的噪声机理,针对强度像噪声抑制问题,提出了一种基于同态滤波和小波域SURE(Stein′s Unbiased Risk Estimate)的激光主动成像图像降噪算法。该方法首先用同态变换将乘性散斑噪声转换为加性噪声;然后在小波域,没有将小波系数看作随机变量,而是以最小化均方误差MSE为目的,将图像降噪过程看作是一个小波系数的加权和,通过SURE获得近似最优的小波系数的权值;最后再作相应的小波逆变换和同态逆变换,得到降噪后的图像。实验结果表明:该方法具有较好的噪声抑制效果,且计算量极小。
In this paper, the noise mechanism of laser active imaging is analyzed. For the problem of intensity image noise suppression, a laser active image noise reduction algorithm based on homomorphic filter and SURE (Stereographic Unbiased Risk Estimate) is proposed. In this method, we first transform the multiplicative speckle noise into additive noise by homomorphic transform. Then in the wavelet domain, we do not regard the wavelet coefficients as random variables. Instead of minimizing the mean square error (MSE), the image noise reduction process Considered as a weighted sum of wavelet coefficients, the weights of approximate optimal wavelet coefficients are obtained by SURE. Finally, the corresponding wavelet inverse transform and homomorphism inverse transform are used to obtain the denoised image. The experimental results show that this method has better noise suppression effect and less computational cost.