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A new technique for finishing the surfaces of friction pairs has been proposed, which, in combination with the original test method, has shown a significant influence of the initial roughness configuration (surface texture) on friction and wear. Two types of finishing processing of the shaft friction surfaces were compared, and it was found that the friction and wear coefficients differ by more than 2–5 and 2–4 times, respectively. Based on a new methodology for analyzing standard roughness parameters, the tribological efficiency criteria (in the sense of reducing friction and wear) are proposed for the initial state of the friction surface of a radial plane sliding bearing shaft relative to the friction direction, which is consistent with its frictional characteristics. Comparison of the laboratory test results with the surface tribological efficiency criteria showed that these criteria are very promising for controlling existing technologies and optimizing new technologies for friction surface finishing in various friction systems. [ABSTRACT FROM AUTHOR]

For the most popular method of scan formation in Optical Coherence Tomography (OCT) based on plane-parallel scanning of the illuminating beam, we present a compact but rigorous K-space description in which the spectral representation is used to describe both the axial and lateral structure of the illuminating/received OCT signals. Along with the majority of descriptions of OCT-image formation, the discussed approach relies on the basic principle of OCT operation, in which ballistic backscattering of the illuminating light is assumed. This single-scattering assumption is the main limitation, whereas in other aspects, the presented approach is rather general. In particular, it is applicable to arbitrary beam shapes without the need for paraxial approximation or the assumption of Gaussian beams. The main result of this study is the use of the proposed K-space description to analytically derive a filtering function that allows one to digitally transform the initial 3D set of complex-valued OCT data into a desired (target) dataset of a rather general form. An essential feature of the proposed filtering procedures is the utilization of both phase and amplitude transformations, unlike conventionally discussed phase-only transformations. To illustrate the efficiency and generality of the proposed filtering function, the latter is applied to the mutual transformation of non-Gaussian beams and to the digital elimination of arbitrary aberrations at the illuminating/receiving aperture. As another example, in addition to the conventionally discussed digital refocusing enabling depth-independent lateral resolution the same as in the physical focus, we use the derived filtering function to perform digital "super-refocusing." The latter does not yet overcome the diffraction limit but readily enables lateral resolution several times better than in the initial physical focus. [ABSTRACT FROM AUTHOR]

A new technique for finishing the surfaces of friction pairs has been proposed, which, in combination with the original test method, has shown a significant influence of the initial roughness configuration (surface texture) on friction and wear. Two types of finishing processing of the shaft friction surfaces were compared, and it was found that the friction and wear coefficients differ by more than 2–5 and 2–4 times, respectively. Based on a new methodology for analyzing standard roughness parameters, the tribological efficiency criteria (in the sense of reducing friction and wear) are proposed for the initial state of the friction surface of a radial plane sliding bearing shaft relative to the friction direction, which is consistent with its frictional characteristics. Comparison of the laboratory test results with the surface tribological efficiency criteria showed that these criteria are very promising for controlling existing technologies and optimizing new technologies for friction surface finishing in various friction systems.

For the most popular method of scan formation in Optical Coherence Tomography (OCT) based on plane-parallel scanning of the illuminating beam, we present a compact but rigorous K-space description in which the spectral representation is used to describe both the axial and lateral structure of the illuminating/received OCT signals. Along with the majority of descriptions of OCT-image formation, the discussed approach relies on the basic principle of OCT operation, in which ballistic backscattering of the illuminating light is assumed. This single-scattering assumption is the main limitation, whereas in other aspects, the presented approach is rather general. In particular, it is applicable to arbitrary beam shapes without the need for paraxial approximation or the assumption of Gaussian beams. The main result of this study is the use of the proposed K-space description to analytically derive a filtering function that allows one to digitally transform the initial 3D set of complex-valued OCT data into a desired (target) dataset of a rather general form. An essential feature of the proposed filtering procedures is the utilization of both phase and amplitude transformations, unlike conventionally discussed phase-only transformations. To illustrate the efficiency and generality of the proposed filtering function, the latter is applied to the mutual transformation of non-Gaussian beams and to the digital elimination of arbitrary aberrations at the illuminating/receiving aperture. As another example, in addition to the conventionally discussed digital refocusing enabling depth-independent lateral resolution the same as in the physical focus, we use the derived filtering function to perform digital “super-refocusing.” The latter does not yet overcome the diffraction limit but readily enables lateral resolution several times better than in the initial physical focus.

• This paper proposes a holographic curved waveguide system for near-eye display. • An iterative algorithm is established based on angular spectrum theory to simulate the whole propagation process and analyze the behavior of light beam in the curved waveguide. • A phase compensation measures for overmodulation during beam propagation in the waveguide have been proposed. • Experiments have proven that the overmodulation can be diluted with the appropriate compensation phase over an effective distance. Generally, current type of waveguide used for near-eye displays is planar waveguide, which belongs to flat panel display. Compared to display system in three-dimensional space, flat panel display limits people's view of the 3-D world and is not conducive to the integration of virtual and reality. This paper proposes a holographic curved waveguide system for near-eye display. In order to analyze the propagation process of light beam in waveguide, an iterative algorithm is established based on angular spectrum theory to get the intensity distribution from each total internal reflection point. According to the simulation results and experimental phenomenon, we have developed phase compensation measures for overmodulation during beam propagation in the waveguide. The research shows that using curved waveguide can achieve beam transmission with less aberration after introducing an appropriate phase compensation in a distance, and it can also achieve beam transmission with lossless energy within a large radius range. Experiments have proven that the final coupling effect is basically consistent with the simulation results, this means that our proposal about curved waveguide has potential application value in near-eye display systems. [ABSTRACT FROM AUTHOR]

• Proposing a fast point-based hologram generation method using high-frequency information extraction. • Using the Gaussian filter to separate high-frequency information and low-frequency information of the 3D objects. • Improving the calculation speed by over 65%. • Combining different algorithms and leveraging their respective advantages. Computer-generated hologram based holographic 3D display is an important development direction of holographic 3D display. However, the heavy amount of calculation affects the generation speed of the holograms, which limits the further development of real-time holographic 3D display. In this paper, a fast point-based hologram generation method using high-frequency (HF) information extraction is proposed. Firstly, an image information processing method based on the Gaussian filter is proposed to separate the HF information and low-frequency (LF) information of 3D object. Then, the HF hologram is calculated by using the novel-look-up-table algorithm, while the LF hologram is calculated by the angular spectrum algorithm. Finally, the final hologram is obtained by overlaying HF hologram and LF hologram. Compared with the traditional method, the proposed method improves the generation speed of the hologram by more than 65%. Moreover, the details of 3D object can be fully reconstructed, and the quality of the reconstructed image is slightly improved with lower speckle noise. Experimental results verify the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

The feature size of holographic diffuser is an important parameter which affects the display resolution when the holographic diffuser is used as an exit-pupil expander device in head up display. However, there is currently a lack of relevant research work on it. Here, we derive the amplitude and phase properties of the scattering light based on a statistical model of the surface undulations of ground glass. Combining with angular spectrum diffraction theory, a method for accurately simulating the speckle pattern is developed. The speckle patterns in the far-field and near-field diffraction areas of light passing through ground glass is calculated, then compared with estimation and experimental results. The comparison shows that the speckle feature size obtained by the traditional estimation method is quite different from the experimental results in the nearfield diffraction area. While the results obtained by our simulation method is in good agreement with the experiment in both near-field and far-filed diffraction areas. This work provides an effective method for the design and preparation of small feature size holographic diffuser elements. [ABSTRACT FROM AUTHOR]