The design of an imaging spectrometer based on forearm compensation optical path multiplexing

The plane diffraction grating has very high diffraction efficiency, so it is widely used in spectrometers. However, since the principal section of the plane grating does not coincide with the section of the diffracted light, a serious spectral smile occurs, causing deviation in the collected spectral and image information, which affects the imaging spectrometer's detection accuracy for the target signal. To address this issue, a design method of an imaging spectrometer based on forearm compensation optical path multiplexing is proposed in this paper. The forearm compensation lens group generates spectral smile in the opposite direction of to the plane grating to correct the spectral smile of the spectrometer. Moreover, the correction conditions for wide spectrum aberrations are derived based on vector geometric relationships. Based on the proposed design method, we have developed a prototype with a spectral range of 0.45 μm–0.9 μm, a spectral resolution of 6 nm, spectral smile and spectral distortion both less than 2.5 μm, and a volume of approximately 65 mm × 40 mm × 40 mm. Finally, the spectral and imaging performance of the prototype is tested.The test results confirm the feasibility of correcting the spectral smile of an imaging spectrometer and the correctness of the correction conditions for the wide spectrum aberrations based on our proposed design method.