Holographic interferometry for measuring displacements of LARES 2 satellite components

Holographic interferometry is an optical technique that allow high resolution full field measurement of displacements. In this work it will be shown the use of a low-cost holography kit to perform holographic interferometry. The use of self-developing holographic film plates makes it easier the realization of holograms but on the other hand it makes very difficult the use of double exposure technique. Real-time holographic interferometry is then used in this paper to quantitatively verify the displacement. The fringes are clearly shown in the screenshots taken during the application of the mechanical displacements. The test item is a plastic ring of the Cube Corner Reflector (CCR) mounting system that will be used for the LARES 2 satellite. The fringe number is quantitatively sound in that the fringe counting represents well the displacement. More difficult was the application of holographic interferometry to measure the displacements due to thermal deformations. The holographic interferometry technique applied to this case is more complicated because heat propagation cannot be completely controlled so that gradients in the air, crossed by the real-time object wave, can destroy the fringes. The paper will present the experimental results obtained by mechanical and thermal deformation of the plastic ring.