Measurement of the boundary shape of a two-dimensional deformed microcavity with forward shadow scattering

We have developed a new surface boundary profiling technique based on forward shadow diffraction that satisfies both requirements of high-precision and applicability for soft columnar objects and have measured the boundary shape of a microscopic liquid jet two-dimensional microcavity with it. We established a reciprocal relation between the forwardly-projected width of an opaque object and the angular width between two adjacent local minima on its diffraction pattern, and an one-to-one mapping formula which enables us to reconstruct the boundary profile from the observed projected width function. Experimental results show that the cross-sectional shape of the liquid jet microcavity can be expressed as a sum of quadrupolar and octapolar components with an accuracy of 0.1 % of radius with those amplitudes aligned under a special relation.