Zhang Jialun, Lin Chao, Ji Zhenhua, Wu Hao, Li Chengliang, Du Bowen, Zheng Yuquan
Appl Opt. 2020 Feb 20;59(6):1715-1725. doi: 10.1364/AO.379390.
Hyperspectral imaging spectrometers with a wide field of view (FoV) have significant application values. However, enhancing the FoV will increase the volume of the imaging spectrometer and reduce the imaging quality, so a wide-FoV spectrometer system is difficult to design. Based on the theory of off-axis astigmatism, we present a method that includes a "prism box," "partial anastigmatism," and a partial differential equation to solve the parameters of a freeform surface. In this method, a compact wide-FoV imaging spectrometer with a freeform surface is designed. The spectrometer is an Offner structure with two curved prisms as the dispersion elements. The primary mirror and tertiary mirror of the Offner spectrometer are an aspheric surface and a freeform surface, respectively, to correct the off-axis aberration of a wide FoV. The ratio of the slit length to the total length of the spectrometer is close to 0.4. In comparison to conventional spectrometers of the same specifications, the total length of the spectrometer is reduced by 40% and the volume by 70%. The compact imaging spectrometer has potential application in the field of space remote sensing. In addition, the design method of the spectrometer provides a reference for the design of other optical systems with freeform surfaces.
具有宽视场（FoV）的高光谱成像光谱仪具有重要的应用价值。然而，增大视场会增加成像光谱仪的体积并降低成像质量，因此宽视场光谱仪系统难以设计。基于离轴像散理论，我们提出了一种方法，该方法包括一个“棱镜盒”、“部分消像散”以及一个用于求解自由曲面参数的偏微分方程。通过该方法，设计了一种具有自由曲面的紧凑型宽视场成像光谱仪。该光谱仪是一种Offner结构，以两个曲面棱镜作为色散元件。Offner光谱仪的主镜和三镜分别为非球面和自由曲面，以校正宽视场的离轴像差。狭缝长度与光谱仪总长度的比值接近0.4。与相同规格的传统光谱仪相比，该光谱仪的总长度减少了40%，体积减少了70%。这种紧凑型成像光谱仪在空间遥感领域具有潜在应用。此外，该光谱仪的设计方法为其他具有自由曲面的光学系统的设计提供了参考。
