This works describes a novel optical refraction index sensor which is based on the analysis of double reflection lecture detection. This process initially identifies the thickness of a semitransparent solid o liquid material by the retro-reflection of a laser diode at 633nm as a function of distance along the device under test with a Z-axis scanner to find the focusing point. This feedback signal brings how far traveled the beam path which is indirectly related with the refractive index at different materials, the data of the thickness at each layer is treating with a geometrical analysis of the beam velocity.