Zhang YangLiu, Wang Xu, Su ZhouPing, Pan HongXiang, Chen XingTao, Zhang WenYu
Appl Opt. 2021 Feb 1;60(4):942-948. doi: 10.1364/AO.411923.
A double seed curve extension (DSCE) method is proposed to design a freeform surface directly in an off-axis reflective imaging system. Compared with the basic seed curve extension (SCE) method, the DSCE can effectively reduce the error of freeform surface construction and improve the imaging quality of the off-axis reflective imaging system. In addition, the method can be employed to design an off-axis reflective imaging system consisting of multiple freeform surfaces with several virtual image points set in advance. In order to verify the DSCE method, three examples are given. One is the off-axis freeform one-mirror system, one is a compact off-axis three-mirror imaging system with two freeform surfaces, and the other is an off-axis reflective system with three freeform surfaces. The modulation transfer function (MTF) of the one-mirror system is greater than 0.9 at 20 lp/mm, which is close to the diffraction limit. The average of the sagittal and tangential MTFs of the second system designed by the SCE and DSCE methods are 0.26 and 0.74 at spatial frequency of 20 lp/mm, respectively. And the MTF of the last system designed by the DSCE method is greater than 0.9 at 20 lp/mm, which is better than that of the SCE method.
提出了一种双种子曲线扩展（DSCE）方法，用于在离轴反射成像系统中直接设计自由曲面。与基本种子曲线扩展（SCE）方法相比，DSCE可以有效降低自由曲面构建的误差，提高离轴反射成像系统的成像质量。此外，该方法可用于设计由多个自由曲面组成的离轴反射成像系统，并预先设置多个虚拟像点。为了验证DSCE方法，给出了三个例子。一个是离轴自由曲面单镜系统，一个是具有两个自由曲面的紧凑型离轴三镜成像系统，另一个是具有三个自由曲面的离轴反射系统。单镜系统在20 lp/mm处的调制传递函数（MTF）大于0.9，接近衍射极限。由SCE和DSCE方法设计的第二个系统在空间频率为20 lp/mm时，矢状面和切向MTF的平均值分别为0.26和0.74。由DSCE方法设计的最后一个系统在20 lp/mm处的MTF大于0.9，优于SCE方法。
