Patent ID: 8496340
Filing Date: 2013-07-30
Classification: G02B

Abstract:
1. A retroreflective element comprising: a solid spherical core wherein the solid spherical core is transparent and comprises an outer core surface, the outer core surface providing a first interface; a first complete concentric optical interference layer having a thickness of up to approximately 600 nm, wherein the first complete concentric optical interference layer is transparent and has (i) an inner surface directly overlying the outer core surface and (ii) an outer surface, the outer surface of the first complete concentric optical interference layer providing a second interface; a second complete concentric optical interference layer having a thickness of up to approximately 600 nm, wherein the second complete concentric optical interference layer is transparent and has (i) an inner surface directly overlying the outer surface of the first complete concentric optical interference layer and (ii) an outer surface, the outer surface of the second complete concentric optical interference layer providing a third interface.