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1

Application for analysis of the multiple coherence function in diagnostic signal separation processes

Wądołowski Mariusz, Pankiewicz Jarosław, Markuszewski Damian

Vibrations in Physical Systems

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2020

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Vol. 31, nr 3

art. no. 2020324

EN

Diagnosing the condition of the machine during its operation by non-invasive methods is most often reduced to measuring the acceleration of vibrations occurring on the housing, as close as possible to the observed element or changes in sound pressure in the immediate vicinity of the machine. For proper inference about the condition of a given machine element, the registered signals should be undisturbed by signals coming from other components and free from external interference. In the case of simple stationary machines, it is quite simple, but in the case of more complex systems, such as a car, which in addition is in motion, things get complicated In the available literature we find examples of the effectiveness of using ordinary coherence function to separate signals from two independent sources[1,2,3]. This work presents attempt to build an algorithm that uses signals from a multi-point measurement system to analyze multiple coherence functions, which allows to separate signals from various sources. It can then get diagnostic information from the signal thus separated. The effectiveness of the algorithm was tested on a model simulating signal mixing, and then using signal coherence function and knowledge of the transmittance function, the signals were separated.

2

Wigner transform approach to dynamic-variable partially coherent laser beam characterization

Jabczyński J., Gontar P., Gorajek Ł.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2020

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Vol. 68, nr 1

141--146

EN

1) Background: the modeling, characterization, transformation and propagation of high-power CW laser beams in optical (including fiberoptic) trains and in the atmosphere have become hot topics in laser science and engineering in the past few years. Single-mode output is mandatory for high-power CW laser applications in the military field. Moreover, an unstationary, dynamic operation regime is typical. Recognized devices and procedures for laser-beam diagnostics could not be directly applied because of dynamic behavior and untypical non-Gaussian profiles. 2) Methods: the Wigner transform approach was proposed to characterize dynamically variable high-power CW laser beams with significant deterministic aberrations. Wavefront-sensing measurements by means of the Shack-Hartmann method and decomposition into an orthogonal Zernike basis were applied. 3) Results: deterministic aberration as a result of unstationary thermal-optic effects depending on the averaged power of the laser output was found. Beam quality determined via the Wigner approach was changed in the same way as the measurements of the beam diameter in the far field. 4) Conclusions: such an aberration component seems to be the main factor causing degradation in beam quality and in brightness of high-power CW laser beams.

3

Simulation of partially spatially coherent light propagation in the near field

Kozacki T., Prytulak M., Jóźwicki R.

Elektronika : konstrukcje, technologie, zastosowania

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2004

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Vol. 45, nr 8-9

284-287

EN

Simulation of partially coherent light propagation in the near field requires a large computer power. New algorithms for the simulation of spatially partially coherent light propagation are proposed, where the necessary computer power is meaningfully decreased. Two partially coherent sources are considered: globally incoherent and Schell-model ones.

PL

Algorytmy opisujące propagację wiązek częściowo koherentnych wymagają znacznych mocy obliczeniowych. Zaproponowano nowe algorytmy obniżające wspomnianą moc dla dwóch źródeł: globalnie niekoherentnych i źródła znanego w literaturze pod nazwą Schell-model.