空间外差光谱技术综合了光栅衍射与空间调制干涉两种技术特点。由于干涉仪胶合与光栅刻划过程中存在误差，使得系统平场与理论设计值存在偏差。本文探讨了空间外差光谱仪系统平场定标的原理，通过干涉条纹频率公式推导出了系统平场定标的基本公式，设计了可调谐激光导入消散斑积分球定标方法及定标装置。针对中科院安徽光机所研制的用于大气CO2精细吸收光谱(1 575 nm吸收带）探测的空间外差光谱仪样机开展了平场定标实验。定标结果表明，仪器的实际平场波长比理论设计值向短波方向漂移了约0.05 nm，满足仪器设计要求。

Spatial Heterodyne Spectroscopy (SHS) is a novel technology which shares the advantages of grating diffraction and spatially modulated interferometry. However, the flat-field of the system deviates its theoretical values due to the errors from interferometric gluing and grating etching. This paper explores the calibration principle of the flat-field of the system for the SHS and derives its basic formula by the interferomatric fringe frequency formula. Then, it discusses the principles of zero frequency calibration and designs a new zero frequency calibration device based on an integrating sphere introduced by a tunable laser for eliminating speckles. A calibration experiment is performed on a SHS prototype for atmosphere CO2 fine absorption spectra in Anhui Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences. The calibration result suggests that the instrument′s zero frequency drifts 0.05 nm toward shortwave as compared to the theoretic value, which meets the design requirements.