Caustics and caustic-diffraction in laser shadowgraphy of a sessile drop and identification of profile near contact line

✍ Scribed by Nengli Zhang; David F. Chao

• Book ID: 104159780
• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 893 KB
• Volume: 35
• Category: Article
• ISSN: 0030-3992
• DOI: 10.1016/s0030-3992(02)00161-5

✦ Synopsis

This paper presents an optical method based on the caustics and caustic-di raction in laser shadowgraphy of a sessile drop to identify and estimate the drop proÿle near the contact line. A parallel laser beam passes through a liquid sessile drop placed on a transparent substrate to produce a shadowgraphic image of the drop on the screen far from the substrate. Along the in ection line of the drop the Gaussian curvature of the wavefront deformed by the drop vanishes, and therefore the in ection line gives caustics in the far ÿeld of the wave, which can be seen on the screen. The neighboring light rays at both sides of the in ection line interfere with each other to form interference fringes at the inner side of the caustics. According to the pattern of the caustics, the drop-proÿle shape can be identiÿed and estimated.