在FRED中通过倒追和正追的方式确定光机系统的关键面、照明面和重要面。照明面是指光学系统中被外界杂散光源照亮的面;关键面是可以从探测中看到的面;关键面和照明面的重叠面即为重要面。重要面是光机系统中一次杂散辐射的主要来源，杂散光的抑制也就是努力减少重要面的数量。 _@E "7<\
`)[dVfxA
Node Name Universe Detector w3#`1T`N
6 Geometry.fastcass.Primary mirror.Reflecting Surface 8.73949821062508 .339134565809722 B
<+K<,S
7 Geometry.fastcass.Primary mirror.Back Surface 0 0 X &\o{w9%
8 Geometry.fastcass.Primary mirror.Edge 0 0 +8UdvMN
9 Geometry.fastcass.Primary mirror.Hole 0 1.00188578326391E-04 JIUtj7 HQ
11 Geometry.fastcass.Secondary mirror.Reflecting Surface 8.71700830771184 .420485262312074 O|UxFnB}
12 Geometry.fastcass.Secondary mirror.Back Surface 0 0 <F=Dj*]
13 Geometry.fastcass.Secondary mirror.Edge 0 4.83222296869994E-09 lA{(8sKN
16 Geometry.fastcass.dewar.FPA.detector array 6.28915267493816 1.09779504189775E-02 l(Cf7o!
18 Geometry.fastcass.dewar.dewar window.Surface 1 8.70787200780954 1.01116317462709 b%nkIP A
19 Geometry.fastcass.dewar.dewar window.Surface 2 8.70787200780954 1.0111548796955 S+FQa7k
20 Geometry.fastcass.dewar.dewar window.Edge 0 8.29493159668308E-06 )C}K R`"
22 Geometry.fastcass.dewar.outer wall.Surf 1 0 4.61988409432715E-05 T _ ~KxQ
24 Geometry.fastcass.dewar.retaining ring.Surf 2 0 5.38379092582642E-05 Dq`~XS*
27 Geometry.main barrel.Surf 3 1.45194696071729E-02 4.48783425373457E-03 '\L0xw4
29 Geometry.Primary baffle.Surf 3 1.44803828118383E-06 .597464630934777 ~ Oh=
31 Geometry.Secondary baffle.Surf 3 .969627358028687 .137673353852238 Ofm5[q =
32 Geometry.Secondary baffle.Surf 4 1.1502279482165E-12 1.42111455012594E-03 wsfysat$
33 Geometry.Secondary baffle.Surf 5 .727220518519163 6.21692034227466E-05 XOxB
(0@
36 Geometry.Secondary struts.strut a.Surf 6 .97011784785664 1.11300844081723E-02 Ea4
* o
38 Geometry.Secondary struts.strut b.Surf 6 5.49202068783075E-14 1.09981876986085E-02 %FlA ":W
40 Geometry.Secondary struts.strut c.Surf 6 .242406839506173 1.09806859127091E-02 Q V/";A3k
=xBT>h;
Node 为几何结构节点数，Universe为空间光源正向追迹的效果，Detector是反向追迹的效果。 J" bD\%
软件打开后，运行critical and illuminated objects脚本，可生成上述结果。
