Immersed imaging spectrometer based on aberration-free holographic grating and imaging method thereof

Abstract

The invention relates to an immersed imaging spectrometer based on an aberration-free holographic grating and an imaging method thereof. A light path of an optical system of the spectrometer is immersed in a high-refractive-index medium, and an optical element sequentially comprises an entrance slit, a spherical reflecting mirror, an aberration-free convex holographic grating and an imaging sensor in the light incidence direction. Light rays obtained by the long entrance slit pass through the high-refractive-index medium and then are reflected by a part of reflecting surfaces in the spherical reflecting mirror, light beams are converged and enter the aberration-free convex holographic grating, and the grating holographic aberration compensates the geometric aberration of the system; and the divergent beam split by the grating is reflected by the other part of the reflecting surface of the spherical reflecting mirror again and then converged on the imaging sensor for imaging. According to the invention, inherent geometric aberration, especially astigmatism, of a holographic aberration compensation system is utilized, an immersed optical path is adopted, the long entrance slit is realized under the limitation of compact volume, and the application requirements of wide field of view and high spectral resolution are met.

Description

technical field [0001] The invention belongs to the technical field of spectral imaging, and in particular relates to an immersion imaging spectrometer based on an aberration-absorbing holographic grating and an imaging method thereof. Background technique [0002] Hyperspectral imaging technology can obtain the image information and high-resolution spectral information of the target scene. The obtained spectral data can be used for material identification and component analysis. application requirements. The convex holographic grating imaging spectroscopy system is based on the Offner concentric structure, which has good symmetry, good optical performance, simple and compact structure, and meets the application requirements of light and miniaturization. [0003] One of the core parameters of an imaging spectrometer is the length of the incident slit. The longer the slit, the larger the field of view of the system. With the increasing demand for wide ground coverage in var...

AI Technical Summary

Problems solved by technology

However, astigmatism is the main geometrical aberration when the incident slit is long, because the diffraction splitting of the convex holographic grating breaks the perfect symmetry of the Offner structure

In order to balance the astigmatism introduced by the asymmetry of the system with a long incident slit, the main technical means are to divide the primary mirror into two and optimize its curvature radius, increase the off-axis distance of the two mirrors, and increase the convex grating The inclination is used to eliminate astigmatism, but this method makes the optical system complicated and difficult to adjust

In addition, introducing a meniscus lens or a free-form surface into the Offner structure can also greatly improve the imaging of the system, but it increases the difficulty and cost of the development of the optical system, making the processing of optical components and the adjustment of the optical system and spectral calibration more difficult, while putting additional load on the system

[0004] In the prior art, the document "Design of Astigmatism Elimination of Convex Grating Imaging Spectral System with Variable Pitch" (Optical Precision Engineering, 2020, Vol.28, No.10, Meihong Zhao) reported a kind of aberration elimination based on variable pitch convex grating Convex grating imaging spectroscopy system with an F number of 2.7, a slit length of 10mm, a spectral resolution of 3.3nm, and a system length of 100mm. The volume is relatively large, and the recording optical path of the aberration-eliminated convex grating is relatively complicated.

Images