An apparatus for a head mounted display, the apparatus comprising: a light source to output lamp light; and a mixing light guide having a substantially rectangular cross-section, the mixing light guide including: a spatial homogenization section having a first end and a second end, the first end coupled to receive the lamp light having a first cross-section profile from the light source and to deliver the lamp light at the second end with a second cross-section profile substantially conforming to the substantially rectangular cross-section of the mixing light guide; and an emission section adjacent to the second end of the spatial homogenization section, the emission section including an emission surface through which the lamp light is emitted with a substantially uniform intensity profile, wherein the emission surface faces a different direction than an input surface of the first end through which the lamp light is received into the mixing light guide, wherein the emission section of the mixing light guide is at least partially defined by a first pattern disposed on a top surface of the mixing light guide opposite the emission surface and a second pattern disposed upon the emission surface, wherein the second pattern comprises a non-uniform pattern of reflective scattering elements and wherein the density of the reflective scattering elements generally increases in the corners of the emission surface relative to a middle of the emission surface. a light source to output lamp light; and a mixing light guide having a substantially rectangular cross-section, the mixing light guide including: a spatial homogenization section having a first end and a second end, the first end coupled to receive the lamp light having a first cross-section profile from the light source and to deliver the lamp light at the second end with a second cross-section profile substantially conforming to the substantially rectangular cross-section of the mixing light guide; and an emission section adjacent to the second end of the spatial homogenization section, the emission section including an emission surface through which the lamp light is emitted with a substantially uniform intensity profile, wherein the emission surface faces a different direction than an input surface of the first end through which the lamp light is received into the mixing light guide, wherein the emission section of the mixing light guide is at least partially defined by a first pattern disposed on a top surface of the mixing light guide opposite the emission surface and a second pattern disposed upon the emission surface, wherein the second pattern comprises a non-uniform pattern of reflective scattering elements and wherein the density of the reflective scattering elements generally increases in the corners of the emission surface relative to a middle of the emission surface. a spatial homogenization section having a first end and a second end, the first end coupled to receive the lamp light having a first cross-section profile from the light source and to deliver the lamp light at the second end with a second cross-section profile substantially conforming to the substantially rectangular cross-section of the mixing light guide; and an emission section adjacent to the second end of the spatial homogenization section, the emission section including an emission surface through which the lamp light is emitted with a substantially uniform intensity profile, wherein the emission surface faces a different direction than an input surface of the first end through which the lamp light is received into the mixing light guide, wherein the emission section of the mixing light guide is at least partially defined by a first pattern disposed on a top surface of the mixing light guide opposite the emission surface and a second pattern disposed upon the emission surface, wherein the second pattern comprises a non-uniform pattern of reflective scattering elements and wherein the density of the reflective scattering elements generally increases in the corners of the emission surface relative to a middle of the emission surface.