Computer Optics

14-24

Authors: Volyar A.V., Bretsko M.V., Akimova Ya.E., Egorov Yu.A.

Theoretical and experimental studies of spectra of optical vortices and orbital angular momentum (OAM) carried by combined singular beams are presented. The combined beams are composed of superposition of Laguerre-Gauss or Bessel-Gauss modes with "resonant" amplitudes depending on a real parameter. If the parameter is an integer, then the OAM of the singular beam is equal to this number. If the real parameter is fractional, then the OAM can be either substantially larger or much smaller than the integer closest to the parameter value. For a non-integer value of the beam parameter, a large number of beams from superposition with integer topological charges contribute to its amplitude. For an integer beam parameter, the contribution to the amplitude is made by only one mode with a topological charge equal to the value of the beam parameter. In the experiment, singular beams with fractional OAMs were shaped using a binary amplitude diffraction grating consistent with the phase function of the singular beam. The measured correlation degree between the initial beam and the beam reconstructed from the vortex spectrum was no less than 90%.

35-41

Authors: Dyshlyuk A.V.

In this paper, we demonstrate resonant phenomena analogous to Autler-Townes splitting, electromagnetically induced transparency and Fano resonances in a resonator based on a single-mode optical waveguide with metallized end-faces. The phenomena are shown to result from strong coupling between the fundamental mode of the waveguide core and the cladding whispering gallery mode. The results obtained open new possibilities in the field of building functional photonic elements using cladding modes of bent waveguides and, in particular, fiber optic refractometers for bio- and chemosensing applications.

54-62

Authors: Kotlyar V.V., Kovalev A.A.

In this work, using an expansion in terms of plane waves, we obtain all six components of the electric and magnetic field vectors for an elliptically polarized optical vortex with an arbitrary integer topological charge. We also obtain expressions for the distributions of the field intensity and the Poynting vector components in the initial plane of this optical vortex. For the particular case of a narrow angular spectrum of plane waves (Bessel beam) and for circular polarization, it is shown that in the presence of inhomogeneous evanescent waves in the initial light field, a reverse flux of light energy can occur near the optical axis. It is also shown that in the initial plane the effect of an “angular tractor” occurs, when at different distances from the optical axis the transverse energy flux rotates clockwise or counterclockwise. Using the obtained general expressions, the light flux for other known exact solutions of the Maxwell equations can be analyzed.

72-77

Authors: Cheng J., Dai W.

This paper presents a framework to automatically read timestamps for surveillance video. Reading timestamps from surveillance video is difficult due to the challenges such as color variety, font diversity, noise, and low resolution. The proposed algorithm overcomes these challenges by using the deep learning framework. The framework has included: training of both timestamp localization and recognition in a single end-to-end pass, the structure of the recognition CNN and the geometry of its input layer that preserves the aspect of the timestamps and adapts its resolution to the data. The proposed method achieves state-of-the-art accuracy in the end-to-end timestamps recognition on our datasets, whilst being an order of magnitude faster than competing methods. The framework can be improved the market competitiveness of panoramic video surveillance products.

83-89

Authors: Vaganov S.E.

An algorithm of dynamic segmentation of sequential frame pairs was proposed. A comparative analysis of segmentation quality when finding shifts and affine inter-frame transformations for the segments was conducted. In addition, we compared the performance of the proposed method with some static segmentation approaches.

99-104

Authors: Li J., Su J., Zeng X.

In the process of the image generation, because the imaging system itself has differences in terms of nonlinear or cameraman perspective, the generated image will face the geometric distortion. Image distortion in general is also a kind of image degradation, which needs the geometric transform to correct each pixel position of the distorted images, so as to regain the original spatial relationships between pixels and the original grey value relation, and which is also one of important steps of image processing. From the point of view of the digital image processing, the distortion correction is actually a process of image restoration for a degraded image. In image processing, in terms of the image quality improvement and correction technology, namely the image restoration, with the wide expansion of digital image distortion correction processing applied, the processing technology of the image restoration has also become a research hotspot. In view of the image distortion issue, this paper puts forward the image distortion correction algorithm based on two-step and one-dimensional linear gray level interpolation to reduce the computation complexity of the bilinear interpolation method, and divide the distorted image into multiple quadrilaterals, and the area of the quadrilateral is associated with the distortion degree of the image in the given region, and express the region distortion of each quadrilateral with the bilinear model, thus determining parameters of bilinear model according to the position of the quadrilateral vertex in the target image and the distorted image. Experiments show that such algorithm in this paper can meet the requirements of distortion correction of most lenses, which can accurately extract the distorted edge of the image, thus making the corrected image closer to the ideal image.

115-122

Authors: Drynkin V.N., Nabokov S.A., Tsareva T.I.

The study proposes video images compression and restoration methods based on multidimensional sampling theory that provide four-fold video compression and subsequent real-time restoration with loss levels below visually perceptible threshold. The proposed methods can be used separately or along with any other video compression techniques, thus providing additional quadruple compression.

132-136

Authors: Tarasov D.A., Milder O.B.

In the work, an approach that uses three-dimensional gradation trajectories in the CIE Lab metric space as analogs of traditional gradational curves is developed. It is shown that the mathematical apparatus of differential geometry of spatial curves describing gradation trajectories can be supplemented by a simpler discrete approach. The possibilities of applying the discrete method for calculating gradation trajectories to the problems of linearization of digital printing systems are demonstrated.