Optical measurement method of contact angle based on interference

Abstract

The invention discloses a contact angle optical measurement method based on microscope focusing. The method comprises the following steps: selecting a substrate plane with liquid drops to be measured; using a monochromatic light source of variable wavelength for illuminating the liquid drops to be measured, generating the interference fringe on the surface of the liquid drops to be measured; counting the mobile number k of the interference fringes in time interval from lambda to lambda+delta(lambda) of wavelength of the monochromatic light emitted by the monochromatic light source of the variable wavelength; obtaining a height h of the liquid drops to be measured according to the mobile number k, the refractive index n of the liquid drops to be measured and the light source wavelength, measuring the look-down diameter d of the liquid drops to be measured in a projection area on the substrate plane along vertical direction with the substrate plane; and obtaining the contact angle theta by combining the height h of the liquid drops to be measured and the look-down diameter. The contact angle of the liquid drops to be measured is easily and accurately measured under downward observation, and the defect of side surface observation of the measured contact angle can be made up.

Description

technical field [0001] The invention relates to the field of optical measurement, in particular to an optical measurement method of contact angle. Background technique [0002] Contact angle is one of the basic parameters reflecting the wetting performance between solid materials and liquid materials, so it needs to be measured accurately and easily. There are many methods of measuring contact angle, such as goniometric method, force measurement method, length method, penetration method, etc. (reference 1: Ding Xiaofeng, Guan Rong, Chen Peizhi. The latest development of contact angle measurement technology [J]. Inspection (Physical Volume), 2008, 02:84-89.). Wherein the preferred method of measuring the droplet contact angle is to observe the droplet profile from the side, and use image processing to analyze the shape to obtain the contact angle (reference 2: Zhang Pei, master's thesis, research on the contact angle measurement method based on image analysis technology, Ea...

AI Technical Summary

Problems solved by technology

However, this method is only suitable for large droplets, and for small droplets, the reflection image formed by the surface to the macroscopic point light source cannot be observed.

[0012] To sum up, so far, although there have been many methods to measure the droplet contact angle by looking down, these methods either involve large and expensive instruments, or require materials with special properties, or add dyes, or measure have a limited range of contact angles, or are not suitable for small droplets, etc.

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