为满足红外双光栅光谱仪波长重复性±0.05 nm的指标要求，设计了光谱仪的波长扫描机构，分析了影响波长重复性的误差源。根据光谱仪结构特点和指标要求，设计了基于丝杠和摆杆的正弦机构作为波长扫描机构，依据凹面光栅扫描原理，推导了光机参数转换公式，分析了各误差源对波长扫描机构的影响。分析结果表明，在丝杠重复定位精度为±1.2 μm时，光谱仪在760~2200 nm波段范围内的重复性应优于±0.05 nm。设计了红外双光栅光谱仪原理样机，并进行了实验验证。以汞灯为光源对其多个特征波长进行7次扫描，计算波长扫描机构在特征波长处的波长重复性。实验结果表明，光谱仪的波长重复性为-0.038~0.041 nm，波长扫描机构满足使用要求。

To achieve the wavelength repeatability ±0.05 nm of the infrared double grating spectrometer, the wavelength scanning mechanism of the spectrometer is designed and the error source that influences the wavelength repeatability is analyzed. According to the structure characteristics and indicator requirements of the spectrometer, the sine mechanism based on lead screw and rocker is designed as the wavelength scanning mechanism. On the basis of concave grating scanning principle, formula from optical parameters to mechanism parameters is derived and the influences of each error source on the wavelength scanning mechanism are analyzed. The analysis results show that the repeatability of the spectrometer in the range of 760~2200 nm should be better than ±0.05 nm when the repeated positioning accuracy of the lead screw is ±1.2 μm. Infrared double grating spectrometer prototype is designed, and experimentally verified. Using mercury lamp as light source, the wavelength repeatability of the wavelength scanning mechanism at the characteristic wavelength is calculated after scanning each characteristic wavelength for 7 times. The experimental results show that the wavelength repeatability of the spectrometer is in the range of -0.038~0.041 nm, and the wavelength scanning mechanism can meet the requirements of the application.