Efficient light engine systems
An angle selective filter for a light projection system including a wavelength conversion material illuminated by an excitation light source in a first wavelength range, the wavelength conversion material re-emitting light in a second wavelength range after excitation by the light in the first wavelength range. 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 [γ 1 ,γ 2 ], 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 [β 1 ,β 2 ], and a third average reflectivity which is high for light having an incidence angle in the range [β 2 ,β 3 ], after reflection on the wavelength conversion material.
1 . 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 α Max , 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 [γ 1 , γ 2 ],
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 [β 1 , β 2 ], and a third average reflectivity which is high for light having an incidence angle in the range [β 2 , β 3 ], after reflection on the wavelength conversion material, and
wherein γ 2 is substantially smaller than β 2 .
2 . The filter according to claim 1 , wherein the first average transmission is larger than 80% such that
T
λ
e
x
=
∫
γ
1
γ
2
T
(
λ
ex
,
θ
)
sin
(
θ
)
d
θ
∫
γ
1
γ
2
sin
(
θ
)
d
θ
≥
80
%
.
3 . The filter according to claim 1 , wherein the second average transmission is larger than 80% such that
∫
β
1
β
2
T
(
λ
,
θ
)
cos
(
θ
)
sin
(
θ
)
d
θ
∫
β
1
β
2
cos
(
θ
)
sin
(
θ
)
d
θ
≥
8
0
%
,
90
%
,
95
%
or
98
%
.
4 . The filter according to claim 1 , wherein the third average reflectivity is larger than 80% such that
∫
β
2
β
3
R
(
λ
,
θ
)
cos
(
θ
)
sin
(
θ
)
d
θ
∫
β
2
β
3
cos
(
θ
)
sin
(
θ
)
d
θ
≥
80
%
.
5 . The filter according to claim 1 , wherein at least one of the angle γ 1 is 0, β 1 is 0, and β 3 is 90°.
6 . The filter according to claim 1 , wherein the angle α Max defining the acceptance cone of the light collection optics is greater or equal to the angle β 2 of the filter.
7 . The filter according to claim 1 , wherein the incidence angle 12 is in the range [0°, 35°].
8 . The filter according to claim 1 , wherein the third wavelength range is a subset of the second wavelength range.
9 . The filter according to claim 8 , wherein the third wavelength range is defined by the wavelength range of at least one of the green or red primary colour of the projection system.
10 . The filter according to claim 1 , wherein the filter is coated on a second side of a transparent substrate, wherein the transparent substrate is configured such that
a first side faces the light collection optics, and
the second side faces the wavelength conversion material.
11 . The filter according to claim 10 , wherein the filter is provided in the projection system at a distance D 1 from the surface of the wavelength conversion material, wherein the distance D 1 is at most 5 mm.
12 . The filter according to claim 1 , wherein the filter is coated on top of the wavelength conversion material.
13 . The filter according to claim 1 , wherein the excitation light source is at least one of a laser light source.
14 . The filter according to claim 13 , wherein the first wavelength range is in the interval [420 nm-500 nm], and the full width at half maximum is in the range of 1 nm to 30 nm, or wherein the first wavelength range is in the interval [350 nm-420 nm] and the full width at half maximum is in the interval of 1 nm to 30 nm.
15 . The filter according to claim 1 , wherein the wavelength conversion material is a photoluminescent material of the type LuAG:Ce or of the type nitride or oxynitride.
16 . The filter according to claim 1 , wherein the wavelength conversion material comprises quantum dots or quantum platelets.
17 . An illumination source for a projector system comprising:
an excitation light source emitting light in a first wavelength range,
a wavelength conversion material provided on a reflective surface, 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,
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 α Max , and
a filter according to claim 1 provided in the light path between the light collection optics and the wavelength conversion material.
18 . The light projection system comprising the filter according to claim 1 or an illumination source comprising:
an excitation light source emitting light in a first wavelength range,
a wavelength conversion material provided on a reflective surface, 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,
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 α Max , and
a filter according to claim 1 provided in the light path between the light collection optics and the wavelength conversion material.