高精度测温拉曼激光雷达光谱仪的光学设计

为了抑制边缘纯转动拉曼光谱成像偏差,提出了一种高精度测温拉曼激光雷达光谱仪光学系统设计。该系统利用非球面透镜组对光谱仪成像球差进行校正,针对光谱仪10mm/nm的线分辨率要求,采用双光栅结构设计并对测温拉曼光谱仪各参数进行光线追迹,拟合得到双光栅的入射角、准直镜焦距和聚焦镜焦距的最优值。将拟合最优化结果代入Zemax软件进行优化分析,结果显示单个成像光谱成像宽度控制在0.771 5mm,间隔0.1nm的纯转动连续光谱成像中心间隔可以达到1mm,满足了线阵探测器对成像质量的要求。通过计算在J=6级的纯转动拉曼后向散射信号对瑞利-米散射信号实现了108抑制,达到了高精度纯转动拉曼激光雷达测温的目的,解决了目前双光栅光谱技术无法达到提取355nm波段纯转动拉曼高光谱精度的要求,对测温拉曼激光雷达的技术发展有着深远的意义。

Optical design and analysis of laser radar spectrometer with high accuracy

This paper presents the optical system design for a high precision, temperature measuring, Raman lidar spectrometer. Using an aspheric lens group on an imaging spectrometer with spherical aberration correction, the results show that the pure rotational Raman spectrum imaging deviation can be effectively suppressed. The 10 mm/nm line resolution requirements for a high precision spectrometer, with a double grating structure design, and the temperature parameters of a Raman spectrometer for ray tracing, are fitted with a double grating incidence angle, and optimal values for the collimating and focusing lens focal lengths. The optimization results were substituted into the Zemax software for simulation analysis, and showed that a single spectral imaging width control in 0.771 5 mm, with 0.1 nm intervals of pure rotational continuous spectrum imaging center spacing, can reach 1 mm. By calculating the purely rotating Raman backscattering signal at J=6, the Rayleigh-Mie scattering signal was suppressed by 10⁸, satisfying the requirements of the linear array detector for image quality, and achieving the high precision of the pure rotational Raman lidar. This has solved the issue in which the double grating spectrum technique could not reach to extract the 355 nm band, which is the accuracy requirement of the high, pure, rotational, Raman spectrum. This indicates that the temperature measurement ability of the Raman lidar technology development is of far-reaching significance, and provides a more accurate basis for the analysis of urban heat island effect, and environmental pollution sources.