Multispectral imaging technology holds significant promise in the field of thermal imaging applications, primarily due to its unique ability to provide comprehensive two-dimensional spectral data distributions without the need for any form of scanning. This paper focuses on the development of an accessible basic design concept and a method for estimating temperature maps using a four-channel spectral imaging system. The research examines key design considerations and establishes a workflow for data correction and processing. It involves preliminary camera calibration procedures, which are essential for accurately assessing and compensating for the characteristic properties of optical elements and image sensors. The developed method is validated through testing using a blackbody source, demonstrating a mean relative temperature error of 1%. Practical application of the method is demonstrated through temperature mapping of a tungsten lamp filament. Experiments demonstrated the capability of the developed multispectral camera to detect and visualize non-uniform temperature distributions and localized temperature deviations with sufficient spatial resolution.

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.

This article presents a spectral thermography method for monitoring the spatial temperature distribution in the molten bath during additive manufacturing of metal parts, along with the experimental setup designed to implement this method. The approach is based on multispectral imaging across four narrow-band spectral channels using a single image sensor. The method was experimentally tested on an electron beam additive manufacturing system. The raw experimental data exhibited characteristic distortions caused by partial material deposition on the protective camera window. A dedicated preprocessing algorithm was developed to compensate for these distortions. Experimental results from electron beam additive manufacturing system demonstrate the feasibility of detecting relative temperature changes during the additive synthesis process. At the selected frame capture rate, periodic temperature fluctuations are observable in the spatial temperature maps, correlating with the specific cladding mode parameters. The overall pattern of the spatial temperature distribution in the mol - ten bath shows a high degree of consistency with theoretical predictions reported in earlier publications. These findings confirm the potential for further application of the proposed approach in temperature regime monitoring during additive manufacturing processes.