Structure design and wavelength accuracy analysis of ultraviolet double grating spectrometer

In order to observe the solar spectrum between 170 nm to 380 nm precisely, an ultraviolet double grating spectrometer with its wavelength repeatability accuracy better than ±0.02 nm has been designed. A wavelength scanning mechanism is the key module of the ultraviolet double grating spectrometer. Mechanical parameters are derived from optical parameters according to the grating dispersion principle. Error sources which influence the spectrometer wavelength repeatability error have been analyzed. According to the analysis results, the repeatability error of the lead screw is the main error source. A wavelength scanning mechanism has been assembled with a ±2 μm accuracy lead screw, and the spectrometer mechanism structure has been designed. Experiments have been carried out with a mercury lamp as light source to verify wavelength repeatability. The experiment results show that the wavelength repeatability of the spectrometer is between -0.005 nm and +0.007 nm, which is better than the required accuracy of ±0.02 nm.