[1] Yang Tong, Duan Yingzhe, Cheng Dewen, . Freeform imaging optical system design: Theories, development and application[J]. Acta Optica Sinica, 41, 0108001(2021).

[2] Wu R, Feng Z, Zheng Z, et al. Design of freeform illumination optics[J]. Laser & Photonics Reviews, 12, 1700310(2018).

[3] Xu Ningyan, Chen Lu, Huang Jing, . Review of design methodology for starting-point of freeform surface imaging optical system[J]. Infrared and Laser Engineering, 51, 20210852(2022).

[4] Wills S. Freeform optics: notes from the revolution[J]. Optics and Photonics News, 28, 34-41(2017).

[5] Meng Qingyu, Wang Hongyuan, Wang Yan, . Off axis three mirror freeform optical system with large linear field of view[J]. Infrared and Laser Engineering, 45, 1018002(2016).

[6] Wu W, Jin G, Zhu J. Optical design of the freeform reflective imaging system with wide rectangular FOV and low F-number[J]. Results in Physics, 15, 102688(2019).

[7] Xie Y, Mao X, Li J, et al. Optical design and fabrication of an all-aluminum unobscured two-mirror freeform imaging telescope[J]. Applied Optics, 59, 833-840(2020).

[8] Chen Bingxu, Liao Zhiyuan, Cao Chao, . Design of the freeform imaging system with large field of view and large relative aperture[J]. Infrared and Laser Engineering, 49, 20200005(2020).

[9] Cheng D, Wang Q, Liu Y, et al. Design and manufacture AR head-mounted displays: A review and outlook[J]. Light: Advanced Manufacturing, 2, 350-369(2021).

[10] Wei S, Fan Z, Zhu Z, et al. Design of a head-up display based on freeform reflective systems for automotive applications[J]. Applied Optics, 58, 1675-1681(2019).

[11] Zhuang Z, Parent J, Roulet P, et al. Freeform wide-angle camera lens enabling mitigable distortion[J]. Applied Optics, 61, 5449-5456(2022).

[12] Reimers J, Bauer A, Thompson K P, et al. Freeform spectrometer enabling increased compactness[J]. Light: Science & Applications, 6, e17026(2017).

[13] Liu Yuxuan, Bauer A, Viard T, et al. Freeform hyperspectral imager design in a CubeSat format[J]. Optics Express, 29, 35915-35928(2021).

[14] Mao Shanshan, Li Yanqiu, Liu Ke, . Optical design of high numerical aperture extreme ultraviolet lithography objective with freeform surfaces[J]. Infrared and Laser Engineering, 48, 0814002(2019).

[15] Takaki N, Papa J C, Bauer A, et al. Off-axis conics as base surfaces for freeform optics enable null testability[J]. Optics Express, 28, 10859-10872(2020).

[16] Takaki N, Bauer A, Rolland J P. On-the-fly surface manufacturability constraints for freeform optical design enabled by orthogonal polynomials[J]. Optics Express, 27, 6129-6146(2019).

[17] Takaki N, Bayer A, Rolland J P. Degeneracy in freeform surfaces described with orthogonal polynomials[J]. Applied Optics, 57, 10348-10354(2018).

[18] [18] Ye Jingfei. Research on the method technique f acterizing freefm optical surfaces[D]. Nanjing: Nanjing University of Science & Technology, 2018. (in Chinese)