Imaging spectrometers enable simultaneous detection of target images and spectra, finding widespread applications in agroforestry monitoring, mineral exploration, and ecological environment surveillance. When comparing convex and concave grating imaging spectrometers, plane grating imaging spectrometers demonstrate superior relative aperture and spectral resolution, making them particularly advantageous for detecting fine spectra of geographical objects, such as monitoring greenhouse gases in specific areas. However, as the field-of-view expands, the inherent spectral distortion of plane gratings increases significantly, adversely affecting the instrument’s spectral response consistency and reducing detection accuracy for edge targets with large field-of-view. To address the challenge of eliminating spectral distortion in ultra-high spectral resolution imaging spectrometers with large field-of-view, this study proposes utilizing prisms with specific vertex angle direction and incidence angle to counteract plane grating spectral distortion. To validate this correction method’s feasibility, an imaging spectrometer featuring ultra-high spectral resolution, large field-of-view, and low spectral resolution is designed.

Initially, the concepts of spectral distortions, including smile and keystone, are introduced to demonstrate the necessity for elimination. Subsequently, a spectral distortion model for the plane grating spectrometer system is established, with calculation formulas for smile and keystone derived from definitions and geometric relationships. A transmissive plane grating spectrometer system example is presented, and spectral distortion calculations are performed. The mechanism of prism correction for smile at central wavelength is then proposed, followed by calculations of spectral distortion in the prism-grating+prism spectrometer system. Incorporating distortion introduced by the focusing system, the minimum achievable smile and keystone for the prism-plane grating imaging spectrometer are analyzed and predicted. Finally, four prism-plane grating configurations are comparatively evaluated based on application requirements, leading to the selection of the spectrometer system structure. An imaging spectrometer incorporating ultra-high spectral resolution, large field-of-view, and low spectral distortion is designed.

The smile introduced by high groove density plane grating is much larger than the keystone (Fig. 3). The prism with specific vertex angle facing chief ray of edge field-of-view can completely offset the smile at central wavelength (Fig. 4). The smile at both edge wavelengths is approximately equal in value but opposite in direction, and the keystone at both edge wavelengths is approximately equal in value and has the same direction (Fig. 5). So, the distortion of image-plane spectrum after correction by prism is just like pillow-shaped distortion (Fig. 6). By introducing a certain amount of negative distortion of the focusing system, the smile and keystone of the spectrometer system can be corrected to a small value at the same time. Four prism-plane grating spectrometer systems including PG structure, P+PG structure, PG+P structure and PG+P+P structure with the same requirements are designed and compared (Fig. 8), and the results show that PG+P+P structure can eliminate spectral distortion better and have medium size (Table 2). In order to verify the feasibility of the correction method, we design an imaging spectrometer based on PG+P+P structure with 0.06 nm ultra-high spectral resolution and 16° large field-of-view corresponding to 84 mm long slit length (Fig. 9). The results show that the imaging spectrometer has good imaging quality (Figs. 9 and 10) and low smile and keystone of about 1 μm (Fig. 12).

This study addresses the challenge of correcting spectral distortion in large field-of-view imaging spectrometers with ultra-high spectral resolution and improving spectral fidelity through investigation of a prism-plane grating spectrometer system. A spectral distortion model establishes the distortion characteristics of the prism-plane grating spectrometer system, revealing the mechanism of prism-based correction for plane grating spectral distortion. Comparative analysis of various prism-plane grating configurations validates the theoretical analysis. Results demonstrate that immersing the plane grating within a prism and incorporating two additional prisms at specific incidence angles effectively reduce spectral distortion to 1 μm for an ultra-high spectral resolution plane grating imaging spectrometer with 0.06 nm spectral resolution and 84 mm slit length, substantially reducing post-processing data requirements.