Measurements of microrelief parameters of industrial products by correlation-spectral processing of their images

Background. Based on the results of the operation of various engineering products, it has been established that the individual features of the microreliefs of their working surfaces largely determine their reliability and durability. In this regard, the development of modern new methods for measuring the roughness parameters of a microrelay for their further use in mechanical engineering is an urgent task at the present time. Aim. The aim of the work is to study and develop an optoelectronic method, new algorithms and software for digital image processing of the studied microreliefs of the mihanic treated surfaces, as a result of which the parameters of the roughness of microreliefs are measured directly during the technological process. Methods. The method is based on computer processing of images of the studied microreliefs. The essence of the method is that the lines of video signals of the microrelief image are considered as the realizations of a random stationary process. Herewith the full Image consists of m such realizations – the number of lines of the image. The number of pixels in the row n corresponds to the width of the image being analyzed. As a result of such image processing, a string matrix of correlation coefficients is obtained, a correlation function, to which the well-known mathematical methods of processing a stationary random process are then applied to find its normalized autocorrelation function. Further, to increase the resolution of the correlation method for estimating the microrelief parameters, spectral analysis of the obtained autocorrelation functions was used. Based on the results of the spectral analysis, the roughness of the studied microrelief is determined with a given probability. Results. A correlation-spectral method for measuring the parameters of microrelief has been developed, which is based on the representation of a halftone image of the surface under study as a set of implementations of a stationary random process. For this representation, correlation functions for the studied microreliefs were calculated and spectral densities for them were determined. It has been established that microreliefs with different roughness differ significantly in spectral densities. The results of applying this method to estimating the parameters of the microrelief of the inner ring of the bearing are presented. Conclusion. The prospects of using the optoelectronic method and digital processing of images of microreliefs of mechanically processed surfaces in order to quickly measure their roughness parameters are shown. An algorithm for calculating the autocorrelation function characterizing the microrelief under study as a set of implementations of a random stationary process, where each implementation is a line of a video signal, has been developed. Then, to increase the resolution of the method, the Fourier transform is applied to the obtained autocorrelation functions and the spectral densities of the autocorrelation functions are calculated. The method of least squares is used to construct the dependence which is used to measure the roughness of the studied microrelief.