The results indicate that with the increase of focal length, the intensity distribution on the focal plane varies from central-dip form to Gaussian distribution.
结果表明：随着聚焦距离的增加，焦面光强分布由中央凹陷状向高斯分布转变。
2
It's action is insulation protection. The body made of high-intensity malleable iron, hot-dip galvanized.