Low-coherence interferometry is a proven and powerful tool that can be applied for precise measurement of the optical path length between optical surfaces and thus, center thickness and air spacing. An advanced measurement setup allows to measure independent from refractive index information. After an initial calibration, the geometrical thickness of single optical components is measured directly.
Furthermore, this technique can also be used to determine the (group) refractive index during production, e.g., of molded lenses, batch testing of optical materials or evaluate the effect of coatings on low Tg materials, to confirm consistent refractive index information and monitor manufacturing conditions. It can also be used for inverse search in the glass catalogue to identify unknown material.
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