Chlorophyll plays a crucial role in the process of photosynthesis and helps to regulate plants’ growth and development. Timely and accurate evaluation of leaf chlorophyll content provides valuable information about the health and productivity of plants as well as the effectiveness of agricultural treatments. For non-contact and high-performance chlorophyll content mapping in plants, spectral imaging techniques are the most widely used. Due to agility and rapid random-spectral-access tuning, acousto-optical imagers seem to be very attractive for the detection of vegetation indices and chlorophyll content assessment. This laboratory study demonstrates the capabilities of an acousto-optic imager for evaluation of leaf chlorophyll content in six crops with different biophysical properties: Ribes rubrum, Betula populifolia, Hibiscus rosa-sinensis, Prunus padus, Hordeum vulgare and Triticum aestivum. The experimental protocol includes plant collecting, reference spectrophotometric measurements, hyperspectral imaging data acquisition, processing and analysis and building a multi-crop chlorophyll model. For 90 inspected samples of plant leaves, the optimal vegetation index and model were found. Obtained values of chlorophyll concentrations correlate well with reference values (determination coefficient of 0.89 and relative error of 15%). Applying a multi-crop model to each pixel, we calculated chlorophyll content maps across all plant samples. The results of this study demonstrate that acousto-optic imagery is very promising for fast chlorophyll content assessment and other laboratory spectral-index-based measurements.

Subject of study. This study investigated a method for designing an optoelectronic system providing simultaneous capture of a single broadband and 15 narrowband spectral images. Aim of study. This study aimed to develop and test a multispectral video camera based on a lens optical system that forms images on a single radiation detector array in the ultraviolet, visible, and near-infrared ranges of the spectrum and has a sufficiently wide field of view and aperture. Method. The proposed solution is based on two configurations of optical systems that correspond to a front aperture stop inverse telephoto lens layout, independently optimized for the ultraviolet and visible/near-infrared channels. The described methodology of lens design makes it possible to provide minimal transverse dimensions, equality of spectral image scales, and the possibility of focusing each lens independently. Main results. The developed multispectral optoelectronic system allows synchronous registration of 16 images: 1 broadband and 15 spectral images in the range of 300–1000 nm with equal 50 nm spacing and 10 nm width of spectral channels. The article presents simulation results, data for aberration analysis, and test images obtained in all 16 channels and demonstrates their high quality. Approbation of the developed lens system was carried out as part of a prototype of a multispectral video camera. The images of a plant sample were registered, and the results of their processing were used to obtain the spectral dependence of the reflection coefficient corresponding to the typical reflection spectrum of plant leaves. Practical significance. The proposed multispectral optoelectronic system provides high quality images in each spectral channel and allows easy channel replacement and tuning to solve the problem of productive collection of spatial-spectral data in precision agriculture, eco-monitoring, medicine, and nondestructive testing.

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.

В статье исследована возможность применения гиперспектральной и RGB-съемки в качестве быстрого и надежного метода определения содержания хлорофиллов для оценки показателей состояния фотосинтетического аппарата. Приведены результаты исследования связей между спектральными характеристиками отражательной способности флаговых листьев пшеницы, характеристиками их цвета и содержанием хлорофилла в условиях наличия и отсутствия затопления. Установлено, что наиболее точная оценка состояния растений может быть построена на основе вегетационного индекса NDVI705, полученного путем обработки гиперспектральных данных.

Subject of study. This study focuses on the acquisition, processing, and interpretation methods and algorithms for spectral images aimed at evaluating surface defects in fruits. Aim of study. The aim of this study is to develop a method for assessing fruit preservation techniques based on the automatic detection and quantitative evaluation of surface defects using imaging spectroscopy. Method. Spectral images were acquired using an acousto-optical imaging spectrometer with a spectral range of 450–850 nm and a bandwidth of 2.5 nm at a wavelength of 650 nm, with a 5 nm step. For processing the spectral images, well-established operations and algorithms for data enhancement and analysis were employed. These included correction for uneven illumination, correction for spatial and spectral inhomogeneity of the optical system’s transmittance coefficient, various image filtering techniques, and threshold binarization. Object classification was based on spectral features. The proposed approach was tested in an experimental study that evaluated the effectiveness of preservation techniques for peaches and nectarines using a treatment that inhibits ethylene production. Main results. A methodology for spectral image acquisition and processing was developed, enabling the automated detection and quantification of surface defects on fruits. An evaluative parameter, defined as the ratio of the defect area to the total surface area of the fruit, was introduced. This parameter allowed for comparison under different experimental conditions. The approving of the approach demonstrated the feasibility of automated defect size determination on fruit surfaces, with a relative error of 11%. Practical significance. The developed data processing algorithms enable regular diagnostics of samples and early identification of defects. The methodology for data acquisition and processing can be extended to devices based on other physical principles for obtaining the spatial distribution of spectral characteristics of objects. This solution complements existing methods for assessing fruit preservation techniques and contributes to the integration of imaging spectrometers into routine practices within the agro-industrial sector.

Vegetation indices (VIs) are a widely adopted and straightforward tool for non-contact estimation of chlorophyll and carotenoid content in plant leaves. However, VI-based method accuracy depends critically on instrument configuration and calibration procedures. This study aimed to evaluate the sensitivity of VI-based pigment assessment to variations in spectral channel parameters (central wavelength and bandwidth) as well as to changes in calibration details defined by the specific VI formula. Pigment content was measured in leaves of Lactuca sativa L. and Cucumis sativus L. at contrasting developmental stages using VI-based reflection spectroscopy across the 450–950 nm spectral range with various protocols and spectrophotometry as the reference method. VI values were calculated with varying central wavelength and widths of spectral bands, and across different VI formulas. Comparative analysis of the obtained measurements revealed that even minor shifts in central wavelengths of less than 20 nm or the use of an alternative index formula could lead to relative errors of 42–77% in the estimation of chlorophylls and carotenoids content, while changes in bandwidth had a much smaller impact, resulting in only 2–5% relative errors. Even with identical parameters of spectral channels, the choice of an appropriate VI and its regression model could introduce significant errors, ranging from 36% to 86%. These findings highlight the critical role of instrument specifications and calibration models in the VIs-based method accuracy and stability, as measurement errors can lead to suboptimal agronomic decisions. Moreover, our study underscores that comparing results from different sensors or platforms can be unreliable unless the channel parameters and calibration details are clearly specified. Therefore, standardization and transparency in VIs assignment is vital to ensure reproducibility and cross-compatibility in non-destructive pigment monitoring by using various devices.