Patent ID: 6231992
Filing Date: 2001-05-15
Classification: G02B

Abstract:
A partial reflector comprising:a substrate having a front surface and a rear surface; anda multi-layer, thin-film coating deposited on one of the surfaces of the substrate, wherein the coating includesa first layer having a prescribed, uniform thickness, wherein the first layer is formed of a prescribed metal oxide,a second layer overlaying the first layer and having a prescribed, uniform thickness, wherein the second layer is formed of a prescribed metal, anda third layer overlaying the second layer and having a prescribed, uniform thickness, wherein the third layer is formed of a prescribed metal oxide,wherein the metal incorporated in the coating's first, second and third layers is the same and consists essentially of niobium, hafnium or zirconium,and wherein the prescribed thicknesses of the first, second and third layers are selected to provide the partial reflector with prescribed, non-zero reflectance and transmittance values that are substantially uniform over a wavelength band of about 400 to 700 nanometers.