Measurement of Liquid Film Thickness by a Fringe Method
Measurement of Liquid Film Thickness by a Fringe Method
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DOI：
10.1080/01457630802290122
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发表时间：
2009-01
影响因子：
2.3
通讯作者：
A. Kariyasaki;Y. Yamasaki;Masazumi Kagawa;T. Nagashima;A. Ousaka;S. Morooka
中科院分区：
文献类型：
--
作者：
A. Kariyasaki;Y. Yamasaki;Masazumi Kagawa;T. Nagashima;A. Ousaka;S. Morooka
人们开发并测试了一种技术，通过反射激光容易形成的干涉条纹图案来测量不透明或厚的单透明板表面上的液滴或液体膜的局部厚度。利用5mw或300mw的激光和滤光片去除激光散斑引起的噪声，通过传统显微镜的物镜提供单色外射照明。根据激光波长和液体折射率计算液体层相邻条纹最大值和最小值之间的高差增量。讨论了平行光照近似下光线追踪的局部倾角估计误差。用条纹法得到的干涉图与激光聚焦位移仪得到的结果吻合较好。为保证现有技术的有效性，进行了测量。结果表明，即使在小尺寸或小接触角的情况下，液滴的接触角也可以精确而快速地得到，并且可以测量在微通道中运动的气泡上的液膜的瞬时三维轮廓。条纹法有足够的潜力获得流中液膜三维特征的更详细信息，如波的产生、破裂和生长以及气泡上的液膜在运动开始时的情况。
A technique was developed and tested to measure the local thickness of a droplet or a liquid film on a surface of an opaque or thick single transparent plate by an interference fringe pattern that was easily formed by reflecting laser lights. Monochromatic epi-illumination through an objective lens of a conventional microscope was provided by a 5 mW or 300 mW laser and a filter to remove the noise caused by laser speckle. The incremental height difference of the liquid layer between neighboring maxima or minima of fringes was evaluated from the wavelength of the laser light and the refractive index of the liquid. Estimation error of a local inclination angle was discussed using ray tracing under parallel illumination approximation. Droplet profiles evaluated from the interferogram that were obtained by the present fringe method agreed well with those by Laser Focus Displacement Meter. Measurement was made to ensure the usefulness of the present technique. It was made clear that the contact angle of a liquid droplet could be obtained precisely and swiftly, even in small size or small contact angle, and that instantaneous three-dimensional profile of a liquid film on a bubble moving in a microchannel could be measured. The fringe method had sufficient potential to obtain more detailed information about three-dimensional characteristics of liquid film in flows such as the generation, breakdown, and growth of waves and the liquid film on a bubble at the beginning of movement.