离焦模糊图像的维纳滤波恢复

Analysis on out of focus error and restoration of blurred image with Wiener filter

为消除离焦误差产生的图像模糊,介绍了基于逆滤波和维纳滤波的离焦模糊图像复原方法。从光学成像原理出发,根据高斯方程计算离焦误差,建立离焦误差与光学传递函数之间的关系。讨论了离焦误差对光学成像系统传递函数的影响。通过建立线性空间不变的模糊模型,构建点扩散函数和光学传递函数,采用与模糊过程相反的处理方法进行图像复原,消除离焦误差造成的图像模糊。测试实验中,对标准样本Lena图像进行了离焦模糊处理,采用维纳滤波算法复原图像,选择不同的离焦半径和维纳滤波参数进行对比。实验结果表明:维纳滤波方法可有效消除离焦模糊;抑制噪声干扰和"振铃效应";可把图像峰值信噪比提高到6dB以上。

In order to recover original image from out of focus blurred image, a method of restoration based on inverse filter and Wiener filter is introduced. The relationship between out of focus error in an imaging system and blurred image is discussed, and the out of focus optical transfer function is presented. The restoration technique is oriented toward mathematically modeling the degradation and applying the inverse process to recover the original image. In image restoration processing, the point spread function （PSF） and optical transfer function （OTF） of defocus is used to restore degraded image with inverse filter or Wiener filter. Using original Lena image in the test experiment, and the descried Wiener filter technique is tested in a simulated experiment on a variety of parameters including out of focus radius and power spectrum ratio. The experiments show that quality improved images can be obtained with the Wiener filter and proper PSF, the restored image shows reduced ringing and noises effects, the peek-signal-to-noise-ratio（PSNR） is advanced above 6dB.