Bildbasierte Bestimmung der räumlichen und zeitlichen Verteilung des Brechungsindex während der Aushärtung von Polymeren in der additiven Fertigung von Optiken

Abstract In many fields and applications a spatially resolved measurement of the refractive index is desirable. This also applies to the additive manufacturing of optical components and is especially true in the special case of photopolymerization of liquid resins by UV irradiation. The key point here is that the resulting refractive index of the optical component to be printed depends on the degree of cure of the polymer. The latter is directly related to the UV irradiance used for curing. Thus, a local variation of the irradiance can enable a local variation of the refractive index of the additively manufactured optical component. In order to set a defined refractive index distribution, it is desirable to measure the refractive index during the photopolymerization of the resin in a temporally and spatially resolved manner. In this article, a method is discussed with which this can be achieved. The basic principle is that the polymer under investigation is brought into contact with a prism and, based on the principle of total reflection at the interface between prism and polymer, the refractive index of the sample can be inferred.