OPTICAL ELEMENT FOR REDUCING STRAY INFRARED LIGHT

An optical element for a head mounted display (HMD) includes an illumination layer, an optical combiner, and an optically transparent layer. The illumination layer is configured to emit infrared light towards an eyeward side of the optical element. The optical combiner is configured to receive reflected infrared light that is reflected by an eye of a user and to direct the reflected infrared light towards an infrared camera. The optically transparent layer is disposed between the illumination layer and the eyeward side of the optical element. The optical element may further include one or both of a confinement layer and an infrared extractor. The confinement layer is disposed on a surface of the optically transparent layer to induce waveguiding of confined infrared light propagating within the optically transparent layer. The infrared extractor is disposed on a side-edge of the optically transparent layer to absorb or frustrate the confined infrared light.