求助]为什么斑点图会这样变化

liufukui

<P>设计了一个扩束镜,焦距为1E08,当像面与最后一面的距离为零时,斑点如下图所示,</P>
<P><img src="data/attachment/forum/dvbbs/2004-5/2004527151953143.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'data/attachment/forum/dvbbs/2004-5/2004527151953143.jpg\');}" onmousewheel="return imgzoom(this);" alt="" />
</P>
<P>但斑点图的直径随着像面与最后一面的距离加大而加大,下图是距离为5000时的斑点图,</P>
<P><img src="data/attachment/forum/dvbbs/2004-5/2004527152020202.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'data/attachment/forum/dvbbs/2004-5/2004527152020202.jpg\');}" onmousewheel="return imgzoom(this);" alt="" /></P>
<P>从图中看出,光斑直径变大,而且出现了光环,为什么会出现这种情况呢?难道是衍射造成的吗?</P>
<P>可是光斑很大呀,直径有12mm.最后说一句,没有任何像差.
</P>

伯爵之光

跟入射光有关，是无限远还是有限距离？应在后端加Paraxial表面设计

liufukui

无限远物距

小马过河

"最后说一句,没有任何像差." show me it.

the layout is needed.