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。 w
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Node Name Universe Detector F*KQhH7Gf
6 Geometry.fastcass.Primary mirror.Reflecting Surface 8.73949821062508 .339134565809722 DzpWU8j
7 Geometry.fastcass.Primary mirror.Back Surface 0 0 _pTcSp 3
8 Geometry.fastcass.Primary mirror.Edge 0 0 :Qge1/
9 Geometry.fastcass.Primary mirror.Hole 0 1.00188578326391E-04 )gdeFA V
11 Geometry.fastcass.Secondary mirror.Reflecting Surface 8.71700830771184 .420485262312074 uY5|Nmiu
12 Geometry.fastcass.Secondary mirror.Back Surface 0 0 )k(K/m
13 Geometry.fastcass.Secondary mirror.Edge 0 4.83222296869994E-09 F+hV'{|w`
16 Geometry.fastcass.dewar.FPA.detector array 6.28915267493816 1.09779504189775E-02 3RtVFDIZA"
18 Geometry.fastcass.dewar.dewar window.Surface 1 8.70787200780954 1.01116317462709 Xe_ <]|
19 Geometry.fastcass.dewar.dewar window.Surface 2 8.70787200780954 1.0111548796955 Lp&nO
20 Geometry.fastcass.dewar.dewar window.Edge 0 8.29493159668308E-06 $4{sP Hi)I
22 Geometry.fastcass.dewar.outer wall.Surf 1 0 4.61988409432715E-05 }+ !"mJx@
24 Geometry.fastcass.dewar.retaining ring.Surf 2 0 5.38379092582642E-05 IH`Q=Pj
27 Geometry.main barrel.Surf 3 1.45194696071729E-02 4.48783425373457E-03 Cu+p!hV
29 Geometry.Primary baffle.Surf 3 1.44803828118383E-06 .597464630934777 @6 "MhF
31 Geometry.Secondary baffle.Surf 3 .969627358028687 .137673353852238 tNY;wl:wp
32 Geometry.Secondary baffle.Surf 4 1.1502279482165E-12 1.42111455012594E-03 d~<$ J9%
33 Geometry.Secondary baffle.Surf 5 .727220518519163 6.21692034227466E-05 |Y!^E % *
36 Geometry.Secondary struts.strut a.Surf 6 .97011784785664 1.11300844081723E-02 d ~ M;
38 Geometry.Secondary struts.strut b.Surf 6 5.49202068783075E-14 1.09981876986085E-02 )]fiyXA
40 Geometry.Secondary struts.strut c.Surf 6 .242406839506173 1.09806859127091E-02 *ak0(yLn)
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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。 "p O
软件打开后，运行critical and illuminated objects脚本，可生成上述结果。
