Efficient light engine systems

An angle selective filter for a light projection system comprising a wavelength conversion material provided on a reflective surface, an excitation light source emitting light in a first wavelength range, the excitation light source being configured to illuminate the wavelength conversion material, the wavelength conversion material re-emitting light in a second wavelength range after excitation by the light in the first wavelength range, wherein said re-emitted light is re-emitted in reflection by the reflective surface, and a light collection optics configured to receive at least a portion of the light re-emitted by the wavelength conversion material within an acceptance cone defined by an angle αMax, wherein the filter is to be provided in the light path between the light collection optics and the wavelength conversion material,

• wherein the filter is configured to have
• a first average transmission which is high for light in the first wavelength range and for angles of incidence in the range [γ1, γ2],
• in a third wavelength range, the filter is configured to have a second average transmission which is high for light having an incidence angle in the range [β1, β2], and a third average reflectivity which is high for light having an incidence angle in the range [β2, β3], after reflection on the wavelength conversion material, and
• wherein γ2 is substantially smaller than β2.