双光栅光谱仪波长扫描机构精度分析

光栅光谱仪作为研究太阳辐射的重要设备之一，其波长扫描机构的精度很大程度上决定了最终测量结果的准确性。从光机系统的光栅参量误差和机械结构误差两方面入手，对丝杠摆杆波长扫描机构展开综合精度分析，依据凹面光栅色散原理，推导出波长λ与摆杆末端沿丝杠方向位移x，摆杆长度l，光栅常数g和入射光线与出射光线夹角半值δ之间的关系。再对等式求导，依据误差叠加原理，计算出在红外工作波段650 nm~2 400 nm范围内，其波长定标误差应不超过±1.227 nm。在实验样机上进行验证，以汞灯为光源拟合出误差与波长的关系曲线，并以氦氖激光器为光源加以验证。实验结果证明了理论计算的正确性，该分析方法为双光栅光谱仪零部件精度指标的确定提供了依据。

Accuracy analysis for wavelength scanning mechanism of double grating spectrometer

Grating spectrometer is one of the most important instruments in studying solar radiation, and accuracy of its wavelength scanning mechanism determines final measurement result. Taking errors from both grating parameters and machining dimensions into consideration, this paper analyzes comprehensive accuracy of wavelength scanning mechanism which is made up of screw and swing. Based on dispersive principle of concave grating, relationships between wavelength λ and displacement of end swing along direction of screw x, swing length l, grating constant g and half angle between incident light and diffraction light δ are derived. Then derivatives of equation are obtain, and wavelength errors are calculated between 650 nm and 2 400 nm and should be no more than ±1.227 nm according to principle of errors stack. Then results are tested on prototype. Fitted curve of wavelength and error can be obtained when taking mercury lamp as light source, and can be checkeded when taking helium neon laser as light source. Results prove correctness of theorectical calculation method, and provide theory evidence in choosing components.