This review considers the modern industrial applications of augmented reality headsets. It draws upon a synthesis of information from open sources and press releases of companies, as well as the first-hand experiences of industry representatives. Furthermore, the research incorporates insights from both profile events and in-depth discussions with skilled professionals. A specific focus is placed on the ergonomic characteristics of headsets: image quality, user-friendliness, etc. To provide an objective evaluation of the various headsets, a metric has been proposed which is dependent on the specific application case. This enables a comprehensive comparison of the various devices in terms of their quantitative characteristics, which is of particular importance for the formation of a rapidly developing industry.

Topological orientation structures in chiral nematic liquid crystals, such as torons, exhibit promising optical properties and are of increasing interest for applications in photonic devices. However, despite this attention, their polarization and phase dynamics during formation remain insufficiently explored. In this work, we investigate the dynamic optical response of a toron generated by focused femtosecond infrared laser pulses. A custom-designed polarization holographic microscope is employed to simultaneously record four polarization-resolved interferograms in a single exposure. This enables the real-time reconstruction of the Jones matrix, providing a complete description of the local polarization transformation introduced by the formation of the topological structure. The study demonstrates that torons can facilitate spin-orbit coupling of light in a manner analogous to q-plates, highlighting their potential for advanced vector beam shaping and topological photonics applications.

This publisher's note contains a correction to Opt. Lett.48, 5463 (2023)10.1364/OL.499478.

A wavelength multiplexing with spectral supercontinuum source in computational ghost imaging is implemented and investigated. In our proof-of-concept experiment, we used two diffraction gratings and one spatial light modulator to form up to 10 independent spectral channels. Registration of data by a spectrometer in such a scheme makes it possible to reduce the time of data acquisition by a factor of ten. It was established that an increase the number of spectral channels from 1 to 10 leads to the increase of the contrast-to-noise ratio by the factor of 2.8. This makes the proposed technique attractive for high-speed demanding applications such as communications and remote sensing.

In this paper, we present a review of the latest results obtained in the scope of ghost imaging using auxiliary multiplex channels. The proposed methods make it possible to increase the speed of image acquisition, as well as eliminate distortions in the signal of a bucket detector. One of the most serious limitations of ghost imaging is the large number of measurements required. During the data acquisition, the optical environment where the observation object is located may change its parameters, which will negatively affect the quality of the reconstructed image. To solve these problems, it is possible to use fast spatial light modulators to set structured patterns and fast detectors. However, such equipment is not available in some spectral ranges and is not able to suppress distortions in the detected signal. In this regard, our team has proposed a number of techniques to solve the problems of a large number of measurements and non-stationarity of the optical medium in ghost imaging systems. First of all, an auxiliary polarization channel method was presented in a ghost imaging system to eliminate distortion in the signal of a bucket detector. Secondly, wavelength multiplexing methods have been proposed in the visible and terahertz wavelength ranges. These methods will make ghost imaging systems more applicable to the tasks of remote sensing and mapping of areas in various spectral ranges.

The measurement of the spatial distribution of the nearly monocyclic terahertz (THz) fields by a raster scanning diaphragm is the widely used approach in THz pulse time-domain holography (PTDH) applied in imaging, optical component design, and wavefront sensing tasks. However, it is historically plagued by a compromise between the balance between the signal-to-noise ratio (SNR) and resolution. To address this challenge and keep both parameters at a high level, we proposed to replace the scanning aperture with the scanning module containing a conjugated diaphragm and lens. This solution allowed us for the first time to experimentally investigate the spatio-temporal dynamics of a Gauss–Bessel beam generated in a widespread low-energy THz system based on a femtosecond laser with a pulse energy of around a dozen nanojoules and a repetition rate of tens of megahertz. In particular, this allowed us to observe the temporal spectrum of the THz Gauss–Bessel field at the beam periphery with SNR ≈0.5, which was not possible using a conventional raster scanning system. A careful numerical analysis of the proposed solution reveals a signal enhancement in the spectral domain of approximately 2.5 times compared to the THz PTDH raster scan detection employing only a diaphragm. Moreover, we have shown that the given solution ensures the temporal profiles remain unaffected by the quadratic phase aberration experienced in conventional raster field scanning with only a single aperture.

Opticalelements based on nanomaterials have gained significant attention due to their potential for advancing research in the terahertz (THz) region. These materials offer compactness and unique properties such as flexibility and stretchability, which enable precise control of wave beams. In this work, we demonstrate an innovative approach to controlling the THz wavefront using spiral zone plates (SZPs) made of single-walled carbon nanotubes (SWCNTs). As a demonstration of the concept, we design the SZP using Laguerre-Gauss mode analysis, and subsequently fabricate and experimentally characterize the resulting vortex beams.

Optical elements based on nanomaterials are becoming major avenues to satisfy the technological requirements of compact, lightweight, and tunable elements of the emerging terahertz (THz) field. A new generation of diffractive components integrating specific geometry with additional features (flexibility, stretchability, rotation, and other approaches for tuning properties) extends the functionality of wavefront control. Here, an innovative approach is demonstrated to control the THz wavefront via a layered composition of spiral zone plates (SZPs) with tunable mutual orientation and scaling. As a proof of concept, the SZP is designed using Laguerre-Gauss mode analysis with further fabrication and experimental characterization of the resultant vortex beams. For each single SZP, a flexible element is proposed based on a thin film of single-walled carbon nanotubes deposited on a stretchable substrate. Thus, this diffraction element can be tuned not only by rotation (along the azimuthal direction), but also by its stretching (in the radial direction). The spatial tuning of the developed SZPs (spiral zone plates) opens up an efficient, convenient, and highly customizable approach for the manipulation of vortex beams. The layered composition of spiral zone plates with tunable mutual orientation and scaling is used to generate and control the THz (terahertz) vortex beam. Proposed optical element is designed using thin film of single-walled carbon nanotubes. In the picture, the different experimental snapshots of THz intensity field is shown near the focus of spiral THz modulator. image

In this paper, we present the results of a comparative analysis of the sensitivity of interferograms to wavefront aberrations recorded with flat and cylindrical reference beams. Our results show that compared to classical linear interferograms based on flat wavefronts, cylindrical interferograms have at least 10% higher sensitivity for radially asymmetric types of aberrations and a 30% decrease in average absolute error for aberration recognition using a convolutional neural network. The use of cylindrical reference beams leads to an increase in the sensitivity of interferograms for detecting medium and strong aberrations.

The paper investigates the sensitivity of interferograms formed using the structured reference beams. The parameters of the reference beam are selected to improve the visualization of aberrations in the interferograms. A study carried out on the use of reference beams with cylindrical wavefronts in the interferograms formation to improve the aberrations recognition using a convolutional neural network. The applying of a cylindrical reference beam instead of a plane one in the interference method for recognition of wave aberrations based on neural networks with Xception architecture makes it possible to reduce the mean absolute error by more than 30%. In this work, for each type of interferogram, the model was trained for 80 epochs, which took about 1.8 hours using GeForce RTX 2070 graphics card. However, after completing this training once, we obtain a model that allows us to make forecasts in 0.055 s for every new interferogram of the same type.

Subject of study. The archival storage of information in the diffraction structure (fringe pattern) of display reflection holograms is studied. Aim of study. The aim is to develop methodologies for assessing the quality of the diffraction structure of display holograms recorded according to Denisyuk's scheme for the quality control of display holograms and their diffraction structures during operation and long-term storage. Method . The methods for estimating the quality of an optical image that can be used in estimating the parameters of a holographic image characterizing the diffraction structure properties are discussed. Main results . The differences in the formation of the diffraction structure of monochrome and color display holograms are considered. When a 30 x 40 cm hologram recorded on a high -resolution Ultimate 04C halide -silver full -color -sensitive photomaterial is exposed to actinic radiation in a wide range of visible spectrum at an illumination level of not less than 1300 lux for more than 25,000 h, the diffraction structure of the hologram degrades, and the contrast of the reconstructed holographic image is reduced by 20%. Photographs of holographic images were quantitatively compared based on the calculation for the average contrast value. The importance of developing methods for quantifying the wave field of an arbitrary -shaped object reconstructed from display holograms is emphasized. The proposed photogrammetry method is recommended for use when characterizing holographic images in the absence of a real object. An algorithm for the analog -to -digital conversion of information contained in display holograms is presented to control changes in the parameters of holographic images both under external influence and during storage. Practical significance . The outlined technique for controlling the parameters of holographic images is an essential tool for addressing challenges related to the archival storage of information within the diffraction structure of display reflection holograms. The described algorithm and its optical implementation scheme offer practical utility for assessing the quality of display holograms and monitoring their diffraction structure throughout storage and operational stages. (c) 2024 Optica Publishing Group

Iterative phase retrieval algorithms from multiple diffraction patterns in the terahertz (THz) frequency range are a promising tool of computational imaging capable of providing high spatial resolution of reconstructed phase images. One of the commonly used algorithms is SBMIR, which employs multiple intensity distributions of the diffraction object wavefield as input data. Com -pared with single-frame methods, the multi-plane approach allows for a faster convergence, but requires time-consuming data acquisition from a receiver positioned at a variety of distances from the object. Previously, we proposed a method for THz data acquisition in a single scan mode, which allows one to quickly obtain an exhaustive set of diffraction distributions. In this paper we evaluate an up-to-date phase retrieval algorithm based on the SBMIR/R-SBMIR method (which utilizes stochastic wavefront propagation) on the experimental data captured by a single-scan technique. Unlike a number of conventional phase retrieval algorithms, which may require a series of numerical experiments for determining optimal intensity distributions from a large dataset, disordered propagation of the estimation wavefront guarantees the high-contrast and high-resolution image reconstruction without pre-setting the parameters. It is shown that the package use of the single-scan technique with the subsequent data processing using the R-SBMIR algorithm has ap-plication potential for automation of the multi-plane phase retrieval in the THz range.

We demonstrate the opportunities of photogrammetry in digitizing information about objects by acquiring a set of photographic images captured from three-dimensional scenes, which are reconstructed from volume reflection holograms. The corresponding requirements are determined for both recording the display hologram and digitizing the information reconstructed from it by photogrammetry. They include the choice of the radiation source used to reconstruct the object wave from the hologram; requirements for object positioning when recording a display hologram relative to the recording medium; and requirements for the glare minimization procedure during the construction of a photogrammetric three-dimensional model.

Multiplane iterative phase retrieval is a promising approach to diffraction imaging, which accurately determines the topographic and internal characteristics of various objects. Nevertheless, the detection systems used often have a limited dynamic range, resulting in overexposure of recorded intensity distributions. In this Letter, we present a novel, to the best of our knowledge, reconstruction algorithm that inpaints saturated areas on the measured intensity datasets and reliably retrieves wave complex amplitude. The proposed technique can be used in various spectral ranges, while we have tested it in the terahertz frequency range, where the problem of sources and detectors is most acute. We show that retrieved amplitude and phase distributions have a quality comparable to that of the images reconstructed from the reference high dynamic range technique. Herewith, the proposed approach seriously simplifies the process of data acquisition, what expands the possibilities in the design of measurement tools and studies of dynamic scenes.