Apochromatic objective for imaging spectral systems of visible, near and short-wave infrared spectrum ranges

   The widespread use of spectral and hyperspectral methods across various scientific and technological fields necessitates increasingly higher optical quality of spectral systems. The challenge of enhancing image quality for hyperspectral systems employed in imaging spectrometry methods is particularly significant. The reliability of reconstructing the spectral characteristics of research objects depends not only on the dispersing element but also on the chromatic and monochromatic aberrations of the optical system. Insufficient correction of chromatic aberrations necessitates the use of additional software and hardware within the spectral system for reliable reconstruction of the spectral characteristics of research objects. Consequently, a crucial aspect of spectral systems development involves finding optimal combinations of glass types and optical scheme architectures to address these issues. The authors examined existing methods for designing optical systems of apochromatic objectives and set and solved the problem of designing the architecture of an optical scheme with the minimum possible set of glass types which is free of chromatic aberrations and allows obtaining high image quality. The study employs well-established methods for computing optical schemes based on the dispersion properties of glass and the composition of optical systems as outlined by M.M. Rusinov. Preliminary theoretical calculation of the optical design provided the initial configuration of the optical scheme and the choice of glass types. Optimization and analysis of the optical system are performed in Zemax CAD. During the optimization of the initial configuration without changing the glass types; correction of chromatic aberrations was achieved in a range significantly exceeding the width determined in the theoretical calculation. An optical scheme of an objective with diffraction-limited correction of chromatic aberrations across a broad wavelength range (0.5–2.3 μm) has been successfully developed. The objective exhibits well-corrected monochromatic aberrations across the entire operational spectral range and qualifies as an apochromat in terms of image quality. The objective design is technologically advanced, comprising six lenses (without aspherical surfaces) fabricated from two types of glass (LZOS catalog). The architecture of the developed optical scheme can serve as a foundation for designing imaging devices for spectral analysis applications, including hyperspectral and multispectral cameras.

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