Technology is provided for an integrated eye tracking and display system for a see-through, near-eye, mixed reality display device. Image data and IR illumination for eye tracking are optically coupled into a respective see-through, planar waveguide positioned to be seen through by each eye in a respective display optical system of the display device. The respective planar waveguide comprises one or more wavelength selective filters positioned to be co-axial with an optical axis of the respective display optical system. The wavelength selective filters direct IR and visible illumination out of the planar waveguide in the direction of the respective eye and direct IR reflections, including reflections from the eye, into the planar waveguide. The reflections are optically coupled out of the waveguide to an IR sensor which generates eye tracking data based on the reflections.