Computer Optics

341-349

Authors: D.A. Bykov, E.A. Bezus, L.L. Doskolovich

We propose a coupled-mode theory for resonant diffraction gratings with a varying period. We consider diffractive structures, in which the reciprocal lattice vector, a quantity inversely proportional to the period, varies linearly in the direction of periodicity. It is shown that optical properties of such a structure essentially depend on the period change rate. On the basis of a comparison with the results of rigorous numerical simulations using the rigorous coupled-wave analysis, high accuracy of the proposed theoretical model is demonstrated. In particular, the developed coupled-mode theory describes the broadening of the resonant peak and the appearance of secondary maxima caused by a non-zero period change rate. The obtained results can be used for the development of linear variable filters based on resonant diffraction gratings with varying parameters.

361-366

Authors: S.S. Stafeev, V.D. Zaitcev, V.V. Kotlyar

In this paper, using the Richards-Wolf equations, we analyze focusing circularly polarized light with flat diffractive lenses. It is shown that as the numerical aperture of the lens increases, the size of the focal spot first decreases and then begins to grow. The minimum focal spot is observed at NA=0.96 (FWHM=0.55λ). With a further increase in the numerical aperture of the lens, the growth of the longitudinal component leads to an increase in the size of the focal spot. When the flat diffractive lens is replaced by an aplanatic lens, the size of the focal spot decreases monotonically as the numerical aperture of the lens increases.

374-380

Authors: R.K. Goncharov, A.D. Kiselev, E.O. Samsonov, V.I. Egorov

In this paper, we continue the study of the quantum cryptographic GG02 protocol, performed using the approach based on the subcarrier waves. We modify the scheme via heterodyne detection and perform security analysis for the full trusted hardware noise model in the presence of collective attacks with finite-key effects. It is shown that the system can potentially distribute the key even if the level of losses in the channel is above 9 dB. This result is consistent with the general technical level and comply with modern standards of practical CV-QKD systems. Finally, the system under consideration fully meets the criterion of composability.

392-397

Authors: A.I. Yurin, G.N. Vishnyakov, V.L. Minaev

Methods for measuring the refractive index of optically transparent dielectric materials are considered. Modified methods based on the methods of minimum deviation and constant deviation are proposed and allow determining the refractive index of triangular prisms with unknown apex angles. In the proposed methods, the angles of light deviation on three faces of the prism are measured, and the refractive index of the material and the prism angles are determined from the solution of a system of equations. To implement the proposed methods, a goniometric system is used. That system was designed to measure angles between the flat surfaces of objects in manual and automated modes. Reference prism samples made of N-SF 1 optical glass, and a hollow prism filled with distilled water are studied. The proposed methods are compared and the measurement error is estimated. It is shown that the modified methods can be used for high-precision measurements of the refractive index in cases where the angles of the prism are unknown, or their measurement is associated with technical difficulties.

407-414

Authors: D.V. Pasynkov, А.А. Kolchev, I.A. Egoshin, I.V. Klioushkin, О.О. Pasynkova

The paper proposes an approach to the segmentation of solid breast lesions and their peripheral areas in ultrasound images. It is noted that identifying the outermost breast lesion structures is an important step for the further lesion classification, directly affecting the final classification of its type. The main feature of the proposed approach is that its implementation takes into account peculiarities of pixel brightness variations in the original image, without using speckle noise filters. The method was tested on a set of ultrasound images of morphologically verified 42 benign and 49 malignant breast lesions marked by a radiologist. The segmentation results were compared with the results of manual marking performed by the radiologist. The average errors in the segmentation of benign and malignant lesion were 5 pixels – for the lesion area and 7 pixels – for the peripheral area, which is insignificant, taking into account the error of manual marking performed by radiologist (3.9 and 4.7 pixels, respectively). The average intersection-over-union (IoU) metrics were 0.82 and 0.80, respectively. The presented results indicate the possibility of using the developed technology in a combination with the system of lesion differentiation.

426-432

Authors: T. Cheng, H. Jin

WSD can effectively remove random noise of a raw image from very low density to ultra-high density fluorescent molecular distribution scenarios. The size of the raw image that WSD can denoise is subject to the used measurement matrix. A large raw image must be divided into blocks so that WSD denoises each block separately. Based on traditional single-molecule localization and super-resolution reconstruction scenarios, wide spectrum denoising (WSD) for blocks of different sizes was studied. The denoising ability is related to block sizes. The general trend is when the block gets larger, the denoising effect gets worse. When the block size is equal to 10, the denoising effect is the best. Using compressed sensing, only 20 raw images are needed for reconstruction. The temporal resolution is less than half a second. The spatial resolution is also greatly improved.

442-450

Authors: A.V. Gaidel, V.V. Podlipnov, N.A. Ivliev, R.A. Paringer, P.A. Ishkin, S.V. Mashkov, R.V. Skidanov

Detailed automated analysis of crop images is critical to the development of smart agriculture and can significantly improve the quantity and quality of agricultural products. A hyperspectral camera potentially allows to extract more information about the observed object than a conventional one, so its use can help in solving problems that are difficult to solve with conventional methods. Often, predictive models that solve such problems require a large dataset for training. However, sufficiently large datasets of hyperspectral images of agricultural plants are not currently publicly available. Therefore, we present a new dataset of hyperspectral images of plants in this paper. This dataset can be accessed via URL https://pypi.org/project/HSI-Dataset-API/. It contains 385 hyperspectral images with a spatial resolution of 512 by 512 pixels and spectral resolution of 237 spectral bands. The images were captured in the summer of 2021 in Samara and Novocherkassk (Russia) using Offner based Imaging Hyperspectrometer of our own production. The article demonstrates the work of some basic approaches to the analysis of hyperspectral images using the dataset and states problems for further solving.

464-473

Authors: M.Yu. Kataev, E.Y. Kartashov, V.D. Avdeenko

With road defects being a key factor in traffic accidents, driver safety, vehicle condition and travel speed, they need to be promptly repaired. The defects include cracks, ruts and potholes on the road surface, and if not repaired in due time, they grow in size very quickly. There are various methods that are used to detect road defects, one of which is a computer vision method. Typically, digital cameras are installed on cars and then the resulting set of images from a given section of the road is processed. This article proposes a technique for obtaining images using unmanned aerial vehicles, which provides the required amount of data to assess the road condition on lengthy road sections. A technique for identifying road cracks and estimating parameters defined in the road traffic regulations is proposed. As a result of the studies, real images are obtained and processed using the method proposed herein, showing high performance and accuracy and indicating the possibility of its future practical uses.

482-490

Authors: S.N. Chukanov

The use of traditional methods of algebraic topology to obtain information about the shape of an object is associated with the problem of forming a small amount of information, namely, Betti numbers and Euler characteristics. The central tool for topological data analysis is the persistent homology method, which summarizes the geometric and topological information in the data using persistent diagrams and barcodes. Based on persistent homology methods, topological data can be analyzed to obtain information about the shape of an object. The construction of persistent barcodes and persistent diagrams in computational topology does not allow one to construct a Hilbert space with a scalar product. The possibility of applying the methods of topological data analysis is based on mapping persistent diagrams into a Hilbert space; one of the ways of such mapping is a method of constructing a persistence landscape. It has an advantage of being reversible, so it does not lose any information and has persistence properties. The paper considers mathematical models and functions for representing persistence landscape objects based on the persistent homology method. Methods for converting persistent barcodes and persistent diagrams into persistence landscape functions are considered. Associated with persistence landscape functions is a persistence landscape kernel that forms a mapping into a Hilbert space with a dot product. A formula is proposed for determining a distance between the persistence landscapes, which allows the distance between images of objects to be found. The persistence landscape functions map persistent diagrams into a Hilbert space. Examples of determining the distance between images based on the construction of persistence landscape functions for these images are given. Representations of topological characteristics in various models of computational topology are considered. Results for one-parameter persistence modules are extended onto multi-parameter persistence modules.