望高手回答,不胜感激

what is the difference in intensity contribution between amplitude-splitting multi-beam fringes and double -beam fringes?why?
when  adjust F-P interferometer,the fringe center is slanting or even out of the field of view ;or the fringe center is in the field center,but the fringe center moves and the cyclic fringle size also changes when moving the eyes,How to explain this phonmenon?
And how to corret it?

中文翻译　
分振幅双光束干涉条纹与多光束干涉条纹的强度有什么不同，为什么？
开始调试f-p干涉仪时，圆纹中心往往偏在一边或者不在视场内，或者在视场的中央，但移动眼睛，圆纹不仅移动，环径也变化，怎么解释现象？如何改正？
望高手．用英文回答，感激感激