利用拉氏算子鉴别散焦模糊图像点扩散函数

对于散焦模糊图像，通常把其散焦点扩散函数近似为圆柱形函数。若能有效地从模糊图像中鉴别出该圆柱形的半径，则等价于求出了散焦模糊点扩散函数。利用拉氏算子对散焦模糊图像进行无方向性的二阶微分，然后求微分图像的自相关，则三维显示的自相关图像上会出现一个环形槽。环形槽由数值为负的一系列相关峰连成，槽底住置连成鉴别 别圆。该鉴别圆以零频尖峰为圆心，直径等于作为散焦点扩散函数的圆柱形直径的两倍。通过插值求和，得到一条鉴别曲线，可以直接鉴别出其直径。这一新的鉴别方法计算 量小，鉴别精度高，抗噪声能力较强。

Identification of the Point Spread Function from the Defocus Image Using the Laplacian Operators

The point spread function（PSF） of the defocus image is approximately columniform. It is reasonable to equate identifying the PSF with identifying th e radius of the column. A new method of identifying the radius is given. There are three important computing steps. The first step is to derivate the de  focus image with a Laplacian operator, which is an isotropic second difference arithmetic operator. The second step is to calculate the autocorrelation   of the derivative image. There must be an annular groove in the 3D show of the autocorrelation image. The bottom of the annular groove is linked by the  autocorrelation peaks whose values are minus. The positions of the peaks link a cycle, whose radius is double that of the PSF column＇s. The third step   is to transform the X-Y coordinates into polar coordinates for the autocorrelation by the interpolation. An identifyication curve will be gained by integral calculus of the angle. The radius of the PSF column can be identified directly from the curve with high precision. This new method has the power t  o resist noise and does not cost much computing time.