基于ASAP软件的二次反射系统的比较

Optical Comparison of Two-stage Reflection Systems Based on ASAP

针对以直径1 000mm、边缘角60°的碟式镜为一次镜的二次反射系统,讨论了不同形状的二次镜(旋转椭圆面型、旋转双曲面型、平面型及旋转抛物面型)的聚光情况.结果表明:当旋转椭圆面型和旋转双曲面型二次反射系统的焦点落在一次镜顶点处时,对旋转椭圆面型二次反射系统,随数值孔径增加,接收板中心的能流密度先增大后又减小,光斑直径减小;数值孔径为0.4时,能量聚光比最大,约为5000倍.旋转双曲面型二次反射系统的能流密度和光斑直径均随数值孔径的增大而减小;数值孔径为0.5时,能量聚光比最大,约为8 990倍,旋转椭圆面型和旋转双曲面型二次镜均适用于二次反射低焦系统.旋转双曲面型二次反射系统聚光比更高,结构更紧凑.对平面型二次反射系统,随焦点位置的升高,接收板中心的能流密度增大;光斑直径几乎不变;焦点相对位置为0.9时,能量聚光比最大,达到21 000倍;适用于高焦二次反射系统.旋转抛物面型二次反射系统随二次镜位置的上升,接收板中心的能流密度增加;光斑直径减小;最大能量聚光比约80倍,适用于低倍二次反射系统.

Four types of two-stage reflection systems were compared,of which the secondary mirror was an ellipsoidal,a hyperboloidal,a planar or a paraboloidal type,respectively.A paraboloidal dish with a diameter of 1 000 mm and a rim angle of 60° was employed as a primary mirror in each system.The final concentrated spots were on the vertexes of the dishes in ellipsoidal and hyperboloidal systems.As to the ellipsoidal system,the flux density on the receiver increases when numerical aperture （NA）＜ 0.4 and then decreases.The spot size decreases with NA increasing.The maximum flux concentration ratio is about 5 000 × at NA=0.4.As to the hyperboloidal system,both the flux density and spot size decrease with NA increasing.The maximum flux concentration ratio is about 8 990× at NA=0.5.The ellipsoidal and hyperboloidal systems are applicable to cases which need low concentrated spots,and the latter has a higher flux concentration ratio with a more compact structure and a smaller secondary mirror.As to the planar system,with the relative location of the concentrated spot increasing,the flux density increases and spot size changes less obviously.The maximum flux concentration ratio is about 21 000 × A planar secondary mirror is suitable for a system which needs a high concentrated spot.As to the paraboloidal system,with relative location of the secondary mirror increasing,the flux density increases and spot size decrease.The maximum flux concentration ratio is 80 ×,which is the lowest among systems mentioned above.A paraboloidal secondary mirror is suitable for a system that requires low concentration ratio.