Investigation of the liquid droplet surface profile features using the laser caustic method

Vedyashkina, A.V., Raskovskaya, I.L., Pavlov, I.N.

Publication in Journal of Optical Technology

For Russian citation (Opticheskii Zhurnal):

Ведяшкина А.В., Расковская И.Л., Павлов И.Н. Исследование особенностей профиля поверхности капли жидкости методом каустик лазерного излучения // Оптический журнал. 2024. Т. 91. № 1. С. 14–24. http://doi.org/10.17586/1023-5086-2024-91-01-14-24

Vedyashkina A.V., Raskovskaya I.L., Pavlov I.N. Investigation of the liquid droplet surface profile features using the laser caustic method [in Russian] // Opticheskii Zhurnal. 2024. V. 91. № 1. P. 14–24. http://doi.org/10.17586/1023-5086-2024-91-01-14-24

For citation (Journal of Optical Technology):

Anastasia V. Vedyashkina, Irina L. Raskovskaya, and Ilya N. Pavlov, "Investigation of liquid droplet surface profile features using the laser caustic method," Journal of Optical Technology. 91(1), 7-13 (2024). https://doi.org/10.1364/JOT.91.000007

Abstract:

Subject of research. Тhe surface profile characteristic of a liquid drop lying on a transparent substrate. The research is based on the optical phenomenon of caustic formation that appears on the screen when droplet is probed by laser radiation. Purpose of the study. Justification of the possibilities of using the caustic laser radiation method to obtain additional information about the microrelief and diagnose the features of the surface profile of a liquid drop lying on a transparent substrate. Method. The employed method of laser caustic involves probing of the studied object with a beam of light and evaluating its characteristics by the geometric parameters of the caustic surfaces formed during refraction or reflection. The key distinction of the caustic method from classical optical methods lies in the ability to determine inflection points of the curve in the heterogeneity model and their locations using the geometric parameters of caustics recorded during the experiment. Main results. The study shows that by using the laser caustic method, it is possible to diagnose the properties of the liquid droplet's surface profile and acquire supplementary data regarding both macro- and micro-relief of the droplet surface when working with established optical techniques. The article presents the results of computer modeling of laser radiation refraction and caustic formation when probing liquid droplets with various surface profile shapes. The emergence of lines with sharply increasing intensity of the light field on the refraction image, which are observed in a series of experiments involving wide collimated laser beams to probe liquid droplets, is explained. Practical significance. The paper demonstrates the new possibilities of applying the laser caustic method in the study of wetting and spreading processes of droplets and films on solid surfaces, that allows to improve of existing optical research methods without the need for expensive equipment.

Keywords:

caustic method, catastrophe optics, laser refractography, liquid boundary layer, contact angle

OCIS codes: 120.5710, 260.2710, 120.4820

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