棱镜-光栅-棱镜型光谱成像系统光学设计

Imaging spectrometer optical design based on prism-grating-prism dispersing device

为实现成像光谱仪系统的直视性和小型化特点,设计一种棱镜-光栅-棱镜(PGP)结合式元件,作为分光系统的成像光谱仪光学系统装置。系统主要包括PGP分光原件、准直系统、成像系统和接收系统。光栅采用体全息相位光栅,可以获得很高的衍射效率,准直和成像镜采用对称式结构,可以有效地消垂轴像差。根据实际指标探测器像元尺寸为20μm×20μm,像元数为512×512,采用双像元合并方法,光谱通道数为148个,狭缝大小为10.2mm×10.2mm,波段在400nm～800nm,物方数值孔径为0.15。分析了PGP光谱成像系统的原理、特点,对参数关系和体全息相位型光栅的衍射效率进行了详细的讨论。分析结果表明:PGP元件在整个光谱范围内理论衍射效率大于0.6,采用ZEMAX软件进行优化设计,得到系统的平均光谱分辨率优于3nm,在截止频率处平均传递数大于0.7,系统总长90mm。

In order to make the imaging spectrometer compact and to be directly viewed, an optical system incoporating prism-grating-prism（PGP） component was designed. The system includes PGP device, collimating lens, imaging lens and receiving device. The system uses volume hologram bragg diffraction grating（VHDG） instead of ordinary ruled grating, which have high diffraction efficiency. Symmetric structure that can eliminate lateral abberations automatically is applied to this system. The requirements of design specification are given, which include 512×512 pixels CCD with pixel size of 20 um ×20 um, 148 spectrum channels,slit size of 10 mm ×0. 02 mm,object NA of 0. 15, and operation wavelength ranging from 400 nm to 800 nm. System concept and features, diffraction efficiency, paraments relationship are discussed. According to analysis, diffraction efficiency is higher than 0. 6 in the whole spectrum range. Using ZEMAX optical optimization software, the MTF of the sysytem is better than 0. 7 at the Nyquist frequency, the spectural resolution is better than 3 nm, and the length of the sysytem is 90 mm.