Roughness Measurements with Polychromatic Speckles on Tilted Surfaces

Abstract

Surface light scattering enables contactless and fast measurements of surface roughness. A surface inclination alters the direction of the scattering beam and thus the measured surface roughness is calculated from the detected intensity distribution. Hence, an accurate sensor–surface alignment is necessary. In order to achieve tilt-independent roughness measurements, a model-based evaluation approach for polychromatic speckle patterns is presented. By evaluating the shape of the superposed speckles, which occur for polychromatic illumination, with regard to the distance to the scattering centre, surfaces with an Sa roughness value in the range of 0.8–3.2 μm are measurable. Experimental investigations demonstrate that the influence of a surface tilt up to ± 1.25° on the roughness measurement is reduced by 90%. As a result, the robustness of the polychromatic speckle roughness measurement is improved, which allows to speed up the adjustment of the measurement system or the surface sample, respectively.

Дифракционная Математическая Модель Лазерного Спекл-Интерферометра Поперечных Смещений Рассеивающего Объекта

“…На интерференции света, отраженного от неоднородных поверхностей, основаны методы измерения и контроля, позволяющие исследовать микросмещения и микродеформации рассеивающих объектов технического и биологического происхождения [1][2][3][4][5][6][7][8][9][10][11][12][13][14], определять степень шероховатости рассеивающей поверхности [12,15]. В ряде практических задач в науке, технике, биомедицинских исследованиях возникает практическая необходимость измерять параметры движения рассеивающих объектов -микросмещения, скорость, ускорение.…”

Diffraction mathematical model of a laser speckle interferometer of transverse displacements of a scattering object

“…Methods of measurement and control based on the interference of light scattered by inhomogeneous surfaces allow investigating microdisplacements and microdeformations of technical and biological scattering objects [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and assessing the roughness degree of the scattering surface [12,15]. In a number of practical problems of science, technology, and biomedical research, there is a practical need to measure the motion parameters of scattering objects, i. e., microdisplacements, velocity, and acceleration.…”

Areal Analysis Investigation of Selective Laser Melting Parts

“…Because the resulting surface quality can considerably influence the properties of the final product, it is vital to understand the causes of surface imperfections to improve the quality of final products [10].…”