(接上期 )3　Ｘ线图像中噪声的表现Ｘ线图像中的噪声的表现 ,如图 5所示。Ｘ线穿过密度均匀的被照体后 ,所成的影像的密度并不是处处均匀的 ,而是起伏波动的。Ｘ线影像密度起伏波动的原因是因为Ｘ线分布的统计涨落、焦点面上的线量分布随着球管两端的管电压变化而变化、记录影 (Continued from the previous period.) 3 Performance of noise in X-ray images The performance of noise in X-ray images is shown in Fig. 5. After the X-rays pass through the evenly-contaminated object, the density of the resulting image is not uniform everywhere, but fluctuates. The reason why the density of the X-ray image fluctuates is that the statistical fluctuation of the X-ray distribution, the distribution of the line quantity on the focal plane changes with the tube voltage at both ends of the tube, and the recording shadow changes.