Patent ID: 8128273
Filing Date: 2012-03-06
Classification: G02B,G02F

Abstract:
1. An illumination system for illuminating a display device, the illumination system comprising: a light-mixing chamber comprising a light-exit window, a rear wall situated opposite the light-exit window, and edge walls extending between the light-exit window and the rear wall, a surface of the rear wall being substantially specularly reflective for specularly reflecting at least a portion of light impinging on the surface of the rear wall, a light source for emitting light into the light-mixing chamber, the light being emitted into the light-mixing chamber in a direction substantially parallel to the light-exit window, a plurality of light out-coupling elements for coupling out the light from the light-mixing chamber, and an angularly reflective filter arranged at the light-exit window, the angularly reflective filter being constituted of a plurality of substantially transparent layers, each layer having a substantially uniform layer-thickness and having a refractive index, each set of two adjacent layers having different refractive indexes, wherein at least one of the transparent layers is a birefringent uniaxial layer having a birefringent symmetry axis arranged substantially parallel to the light-exit window.