Computer Optics

5-12

Authors: V.V. Kotlyar, A.G. Nalimov, S.S. Stafeev, L.O'Faolain, M.V. Kotlyar

We designed, numerically simulated, fabricated and characterized a thin metalens in an amorphous silicon film. The lens has a diameter of 30 µm, a 633-nm focal length equal to the incident wavelength, a 220-nm period of the subwavelength features, and a 110-nm relief depth. The lens simultaneously controls the phase and polarization of the incident laser light, transforming linear polarization into the radial one and generating a sharp focus. The metalens was fabricated using electron lithography and reactive ion etching. The focal spot obtained from an incident linearly polarized Gaussian beam of wavelength λ measured 0.49λ and 0.55λ on the x- and y-axes. This is a record-breaking focal spot ever obtained using metalenses. Experimental results agree well with the numerically simulated focal spot size of 0.46λ and 0.52λ.

22-29

Authors: V.V. Kotlyar, A.A. Kovalev, A.P. Porfirev, E.G. Abramochkin

We theoretically and experimentally study asymmetric Gaussian optical vortices generated via diffracting a Gaussian beam by an off-axis spiral phase plate or amplitude "fork" hologram. It is shown that depending on the magnitude of the off-axis shift the laser beam can acquire a crescentshaped cross-section, which rotates on propagation. We obtain an analytical expression for the orbital angular momentum (OAM) of such a beam, which appears to be fractional. We show that with increasing off-axis shift, the OAM decreases parabolically. The experimental results are in qualitative agreement with theory and numerical simulation.

37-45

Authors: R.A. Shatalin, V.R. Fidelman, P.E. Ovchinnikov

In this paper, we propose novel method for abnormal behavior detection in the video surveillance. The method constructs a normal behavior model using training samples, which makes possible application in a wide range of conditions and scenes. The method was tested in controlled and real conditions. The result shows that the method can be used to detect abnormal behavior in simple and crowded scenes.

59-66

Authors: V.B. Nemirovskiy, A.K. Stoyanov

In this paper a multi-step algorithm for clustering face images is proposed. This algorithm is designed to split a collection of images into groups of similar images. The algorithm is based on clustering the proximity measures between brightness-based segmented images. As proximity measures, the Euclidean distance and the Kullback-Leibler distance were used. Brightness-based image segmentation and clustering respective proximity measures were carried out with the help of a software model of a recurrent neural network. Results of experimental studies of the proposed approach are presented.

79-87

Authors: N.I. Evdokimova, A.V. Kuznetsov

Embedding of duplicates is one of commonly used methods of image forgery. During this process, an image fragment is copied and pasted to another position in the same image. This is performed to conceal some important part of the image. A copy-move forgery detection algorithm aims to recognize duplicated areas in the image. This algorithm is based on calculating the characteristics in a sliding or overlapping window. In this paper, we compare the performance of copymove detection algorithms that utilize a local binary pattern, a local ternary pattern, a local derivative pattern, and some extensions thereof. A distinctive feature of the used characteristics is their resistance to distortions inserted into the copy, such as linear contrast enhancement and impulse noise. This method also has low computational complexity.

95-102

Authors: I.G. Palchikova, E.S. Smirnov

Influence of the analog-to-digital conversion of an input signal from a sample onto the color rendition of a colorimetric device is studied. It is shown that irrespective of the light source choice, a specific systematic quantization error is introduced to the color rendition. We analyze the quantization error for a color photomatrix with a resolution of 8 bits per channel. An algorithm for finding the interval of values of the dominant wavelength and the color saturation of the sample is developed. It is shown that the similarity of two colors in a sample can be estimated by means of the Jaccard similarity coefficient. The spectral dependence of the intervals of color parameters, calculated from digital images, is found by means of a computing experiment. It is found that lower-brightness colors have a larger interval and are calculated with a lower accuracy. A hypothesis explaining the emergence of MacAdam ellipses on the chromaticity diagram is offered, namely the coding process of the visual neural signals can include procedures similar to the analog-to-digital conversion.

110-117

Authors: P.V. Yarashevich, R.P. Bohush

In this paper, a classification algorithm of parking space images is proposed to improve the accuracy of parking space classification, which can be used in smart parking management systems based on video surveillance. The descriptors of a parking space image are formed on the basis of a histogram of oriented gradients by performing the following steps: computation of vertical and horizontal gradients of the original parking space image, computation of the modulus of the gradient and orientation vectors, the gradients are then accumulated into separate cells according to their orientation, the cells are united into blocks, and the orientations of block's cells are normalized. A support vector machine is used to classify the descriptors of the parking space. The purpose of the research was to determine the most efficient parameters of the parking space descriptor and a kernel function. The paper presents the results of experiments.

126-133

Authors: I.M. Kulikovskikh

This paper considers a problem of improving the accuracy of identifying human activity in buildings based on an ecological feature space. To solve this problem a model of logistic regression was implemented on the assumption of the unstable estimation of logistic regression parameters for near linearly separable classes. To reach a compromise between the presence of outliers and the accuracy of recognition an algorithm of anomaly detection was proposed. Computational experiments confirmed the effectiveness of the algorithm and its theoretical consistency.

139-141

Authors: N.L. Kazanskiy

At the Editorial Board's request I summarize interim results achieved in pursuing tasks the Editorin-Chief, academician Victor Soifer formulated in the article "Quo vadis" (Computer Optics, 2014, Vol. 38, No. 4). I analyze results the journal has attained in key bibliometric indicators in the Scopus database by the end of 2015. I compare these indicators with those of journals covering similar topics. I also notify the journal's readers and authors on some Editorial Board's events scheduled for 2017.