一种基于双边滤波的4f光学系统图像去噪方法

An Improved Denoising Method for 4f Optical System Based on Bilateral Filter

在采用相干光源照明的常规4f光学系统中,输出图像极易受到镜头及CCD上的灰尘污点的影响从而造成图像降质。针对该问题,将图像降质原因划分为加性随机噪声、污点、光源不均匀性影响以及系统的低通特性,提出一种简化系统模型。利用系统输入全白图像的输出结果作为先验信息,在假定一次实验中污点和光源保持不变的基础上,确定其分布。提出一种改进的自适应双边滤波算法,以达到实现去除噪声和污点的目的。基于光学实拍图像和人工合成图像的实验表明,该算法能够在保持图像细节的同时较好地去除噪声,进而恢复图像,实现主观视觉质量和峰值信噪比(PSNR)的提高;同时在污点污染严重的情况下该算法具有较好的稳健性。

In optical 4f system with coherent illumination source, the output images are easily contaminated by dusts and spots in the surface of lens and charge coupled device （CCD）. With the image degradation factors being classified by additive stochastic noise, spots, illumination ununiformity and system low-pass characterization, a simplified model is proposed. The output result is used as apriori information when the input is a full white image to calculate the distribution of spots and illumination ununiformity of which stabilization is assumed in an experiment. An improved adapted bilateral filter is therefore introduced to denoise and remove spots. The optical and synthetic image experiments show that the proposed method can effectively reduce noise and restore image with edge sharpness being preserved. The robust characterization of the proposed method is embodied by the simulation results even under the serious spot-contamination circumstance.