Influence of the light source on the liquid optical element planarity measurement

Abstract

The liquid variable focus lenses and mirrors are extensively studied for its variety of applications nowadays because it presents one of the simplest ways for applications as varying optical elements. Instead of other principles the liquid lenses and mirrors can be easily operated by changing the pressure pushing the liquid in and out of the base to change its surface curvature. In case of small diameter optical elements the surface curvature is given by its aperture diameter, applied pressure, and surface tension of the liquid. This feature enables to use such a variable optical element for fine surface tension measurement of small volume of the liquid sample, when the optical element, diameter, and pressure are measured. We are focused on surface tension measurement of small sample of liquid water under supercooled conditions by use of pressure measurement and optical identification of free liquid meniscus planarity. We developed a measurement stand with planar meniscus shape determination by its confocal visualization. We tried different light sources for 0.3 mm diameter meniscus illumination. We discuss an influence of the light source on the liquid meniscus optical element planarity measurement.