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This article discusses approaches for expanding the dynamic range of measuring systems by implementing phase triangulation methods and structured illumination. These systems are designed for the high-precision measurement of the geometric parameters of complex profile products with arbitrary light-scattering surface properties. A method for expanding the dynamic range of thea measuring system is proposed, which is based on the automatic adjustment of the photodetector exposure duration, redundant collection of experimental data, and complex regression analysis. The results of experimental studies on the efficiency of the proposed method are presented. It has been demonstrated that the classical approach to interpreting images obtained using a photodetector with a fixed exposure duration almost always causes a large measurement error in the geometric parameters of a surface with a wide range of light-scattering properties. At low exposure values, the error in measuring the geometric parameters of the surface increases in the dark area, where the signal level is substantially weaker compared to the light areas of the measured surface. At high exposure values, the error in measuring the geometric parameters of the light area of the surface increases because the signal is outside the dynamic range of the photodetector. For the measured geometric parameters of surfaces with different light-scattering properties, the use of a photodetector with an extended range enables achieving a measurement error less than or approximately equal to the error of a measuring system containing a photodetector with a fixed exposure. Expanding the dynamic range simplifies automated measurements because there is no need to further optimize the photodetector parameters for the light-scattering properties of the surface of the measured object. [ABSTRACT FROM AUTHOR]

The study uses phase triangulation methods to examine the development of image processing algorithms for measuring a three-dimensional (3D) surface profile. An algorithm is proposed for decoding images of an object in structured light based on an iterative search for the minimum deviation of the model function using measurement results and compensating for the nonlinearity of the transceiver path of the measuring complex. A distinctive feature of the proposed method is that the search for the model function is desired in the form of a second-degree polynomial, ensuring the stability of the method against nonlinear distortions caused by power-law transformations of the transceiver path. The interval search method is used to reduce algorithmic complexity qualitatively. The proposed algorithm provides a stable search for the value of the initial phase shift in object images, is resistant to noise and nonlinear distortions, and allows image processing in 3D scanning systems based on triangulation methods using structured illumination and phase triangulation. Thus, the algorithm will be useful for data processing during the operation of measuring systems with a nonlinear transceiver path and measurement time constraints. [ABSTRACT FROM AUTHOR]

This article describes the three-dimensional (3D) object geometry measurement systems based on phase triangulation and binary cyclic code methods. When it is required to adapt system elements to environmental conditions, such system configuration difficulties, which arise under nonstandard measurement conditions, were analyzed. To optimize the parameters of the specified measurement system, quantitative estimates of the system configuration quality are proposed based on the results of measuring the 3D geometry of the object and intermediate measurement data. Algorithms for calculating the quantitative estimates of the measurement system quality were developed. A software package consisting of two programs was created, which implements the processing and visualization of the results by measuring the 3D geometry of an object and intermediate measurement data and displaying the quantitative estimates of the measurement system quality on the monitor. The software package was tested when configuring a system for measuring the 3D ice build-up geometry on a stand to study the effects of icing on the reduced models of wind turbine functional elements. The measurement system was set to a characteristic measuring volume of 85 × 67 × 25 mm3. The frequency of the modulating signal and the parameters of the optical system were optimized, namely, the relative position and focal distances of the source and receiver of optical radiation, duration of exposure, and amplification of the analog signal of the receiver. The measurement error of the 3D geometry was 9 μm. For a measurement system of the 3D geometry of an object using the methods of phase triangulation and binary cyclic codes, the possibility of configuration using the developed software package was confirmed. The software package can be used in fields where it is required to adapt the parameters of a 3D geometry measurement system using phase triangulation and binary cyclic code methods to environmental conditions, such as wind and hydraulic power engineering and hot metallurgy industry. [ABSTRACT FROM AUTHOR]

The article presents the application of optical methods for measuring the parameters of three-dimensional objects. It also discusses strategies for decoding phase images in the presence of additive interference and a limited dynamic range of a photodetector. The existing methods for decoding phase images introduce nonlinear distortions and systematic error into the measurement results under such conditions. A phase triangulation method with statistical data filtering is proposed for measuring the three-dimensional profile of an object under random additive interference with a limited dynamic range of a photodetector, which avoids systematic distortions of the measurement results. The method is based on adaptive filtering and statistical analysis of the intensity distribution in the recorded phase images. The error of the method of decoding phase images was analyzed analytically using statistical data filtering and threshold filtering. The proposed method can decode data in systems for measuring three-dimensional geometry that implements the phase triangulation method. [ABSTRACT FROM AUTHOR]

The vortex breakdown bubble in the confined flow generated by a rotating lid in closed containers with polygonal cross sections was analysed both experimentally and numerically for the height/radius aspect ratio equal to 2. The stagnation point locations of the breakdown bubble emergence and the corresponding Reynolds number were determined experimentally and in addition computed numerically by STAR-CCM+ CFD software for square, pentagonal, hexagonal, and octagonal cross section configurations. The flow pattern and the velocity were observed and measured by combining the seeding particle visualization and the temporal accuracy of laser Doppler anemometry. The vortex breakdown size and position on the container axis were determined for Reynolds numbers, ranging from 1450 to 2400. The obtained results were compared with the flow structure in the closed container of cubical and cylindrical configurations. It is shown that the measured evolution of steady vortex breakdown is in close agreement with the numerical results. [ABSTRACT FROM AUTHOR]