图像重建算法中的窗函数研究

对广角扇束扫描模式下的图像重建算法进行了研究．在引入实验的七种典型窗函数中，有限带宽、三角形窗以及余弦窗是卷积窗函数比较理想的选择．在图像重建，选择有限带宽窗时有较好的空间分辨率，三角形窗时有较好的密度分辨率。选择余弦窗时是空间分辨率与密度分辨率两者的折衷；从窗函数的频谱角度考虑。可用于图像重建的一个良好的卷积窗函数应该具备以下条件：（1）最小的3dB带宽B，即最小的主瓣宽度；（2）最小的旁瓣最大峰值A；（3）最大的旁瓣峰值衰减速度D．通过实验，验证了基于窗函数的卷积反投影图像重建算法可以有效地提高重建图像的质量．

Research on windows function of the algorithm in the image reconstruction

The main aim of convolution projection is to remove the noise interference introduced during the scanning process.Because the noise level of scan data is different for different structure characteristics of an inspected object,it must select corresponding convolution functions according to the requirements of inspection in reality.Convolution back projection can eliminate the edge sharpness effect of pure back projection,compensate the high frequency in projection and reduce the density of projection center,as well as ensure the edge clearness of a reconstructed image and well internal distribution.During image reconstruction,Band-limit window results in good space resolution,Triangle window results in good density resolution,and Cosine window is the compromise for space and density resolution.From the point of frequency spectrum of a window function,an ideal convolution window function for image reconstruction should meet the following requirements:(1) Minimum 3db band width B,means minimum main lobe width.(2) Minimum side lobe maximum value A.(3) Maximum attenuating speed D of side lobe peak value.The windows function method ameliorates the process of image reconstruction,which can improve the quality of image reconstruction.The entire procedure from data acquisition to image reconstruction on a computer was completed.Experiment results clearly demonstrate that windows function can efficiently improve the quality of image reconstruction.