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Aiming at the requirement of high-precision spectral measurement of transient light source, pulse laser wavelength and spectral resolution in pm order and flash duration in ns-ms order, according to the working principle of the Czerny-Turner spectrometer, a cross-asymmetric optical system of Czerny-Turner spectrometer with a spectral range of 800nm-1800nm is designed. Through the design requirements of resolution and spectral range, the light splitting scheme of scanning grating tower with three gratings spliced is determined. The initial structure calculation includes the calculation of single-shot spectral range, characteristic wavelength and scanning angle, focal length and aperture of collimator, focal length and aperture of focusing mirror. Then, according to the above calculation results, the Zemax optical design software of Zemax Company is used to establish multiple structures to simulate the rotating scanning of grating tower, so as to realize the grating and splitting of spectrum and carry out the simulation optimization of the system. In order to correct the aberration of optical system of spectrometer, x-y polynomial free-forms surface is introduced into the optical system, which is called corrective mirror. The design results show that the optical system of the spectrometer meets the design requirements and has excellent performance. Under the conditions of slit width of 25 μm, grating constant of 0.8333 μm/ line, F Number 4.6, the optical system of the spectrometer can achieve a resolution better than 0.1 nm at a center wavelength of 800nm. This design method is also applicable to the structural design of other wavebands, and has guiding significance for the design of broadband grating spectrometer.
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