Luminaire with light exit window

1 . A luminaire, comprising

at least one light source arranged to emit light source light,

a light exit window, wherein the emitted light source light is arranged to exit the luminaire through the light exit window as luminaire light,

wherein the light exit window is configured to influence or modify the luminance, L, of the light source light, for generating a profile of the luminance, L P , of the luminaire light as a function of a length dimension, x, of the light exit window, defined from a center of the light exit window to a periphery of the light exit window, wherein the profile of the luminance, L P , at least comprises

a first interval, x 1 , of the length dimension, x, comprising a step function, S(x), of the luminance, L P , with a first gradient, G 1 =dL P /dx,

a second interval, x 2 , of the length dimension, x, adjacently arranged the first interval, x 1 , wherein the second interval, x 2 , comprises a function, F(x), of the luminance, L P , with a second gradient, G 2 =dL P /dx, and

a third interval, x 3 , of the length dimension, x, adjacently arranged one of the first interval, x 1 , and the second interval, x 2 , comprising a nominal level, L n (x), of the luminance, L P , with a third gradient, G 3 =dL P /dx,

wherein one of

sgn

⁢

(

G

1

)

=

-

1

,

sgn

⁢

(

G

2

)

=

+

1

,

and

⁢

❘

"\[LeftBracketingBar]"

G

1

❘

"\[RightBracketingBar]"

>

G

2

>

❘

"\[LeftBracketingBar]"

G

3

❘

"\[RightBracketingBar]"

,

and

sgn

⁢

(

G

1

)

=

+

1

,

sgn

⁢

(

G

2

)

=

-

1

,

and

⁢

G

1

>

❘

"\[LeftBracketingBar]"

G

2

❘

"\[RightBracketingBar]"

>

❘

"\[LeftBracketingBar]"

G

3

❘

"\[RightBracketingBar]"

,

is fulfilled,

and wherein the profile of the luminance L P in the direction from its center of the light exit window to the periphery of the light exit window comprises a change in luminance, L, from a first luminance, L 1 , via the step function, S(x), in luminance comprising at least one of a maximum step luminance L smax , and a minimum step luminance L smin , to a second luminance, L 2 , wherein L 1 , L 2 >L smin and L 1 , L 2 <L smax .

2 . The luminaire according to claim 1 , wherein the step function, S(x), in luminance comprises the maximum step luminance L smax , and the minimum step luminance L smin , and the profile of luminance L comprises a sequence in luminance L 1 , L 2 , L smin , and L smax from center to periphery of the light exit window of either L 1 −L smin −L smax −L 2 or L 1 −L smax −L smin −L 2 , wherein L smax >L 1 , L 2 >L smin .

3 . The luminaire according to claim 1 , wherein the light exit window comprises a pattern configured to influence or modify the luminance, L, of the light source light into luminaire light.

4 . The luminaire according to claim 3 , wherein the pattern is defined by a distribution of variable light transmission of the light exit window along the length dimension, x, thereof.

5 . The luminaire according to claim 3 , wherein the pattern is defined by a distribution of variable texture of the light exit window along the length dimension, x, thereof.

6 . The luminaire according to claim 3 , wherein the pattern is defined by at least two portions, P i , of the light exit window, having a respective reflectivity, R i .

7 . The luminaire according to claim 3 , wherein the light exit window comprises at least one of a cover element and a foil comprising the pattern.

8 . The luminaire according to claim 1 , wherein the light exit window comprises an optical element configured to influence or modify the luminance, L and/or L P , of the light source light and/or luminaire light via beam shaping of said light.

9 . The luminaire according to claim 1 , wherein,

associated with a direction, DR, of the length dimension, x, of the light exit window, defined from the center of the light exit window to the periphery of the light exit window,

sgn

⁢

(

G

1

)

=

-

1

,

sgn

⁢

(

G

2

)

=

+

1

,

and

⁢

❘

"\[LeftBracketingBar]"

G

1

❘

"\[RightBracketingBar]"

>

G

2

>

❘

"\[LeftBracketingBar]"

G

3

❘

"\[RightBracketingBar]"

,

is fulfilled,

and wherein a first portion of the light exit window, defined around the center thereof, has at least one first radial dimension, Ra, comprising one of

the second interval, x 2 , and the third interval, x 3 ,

and

the third interval, x 3 .

10 . The luminaire according to claim 9 , wherein the at least one first radial dimension, Ra, is defined by the first interval, x 1 , whereby at least one of the first interval, x 1 , and the periphery of the light exit window forms a closed loop.

11 . The luminaire according to claim 9 , wherein the first portion has a first area, A 1 , wherein a first ratio, R 1 , between the first area, A 1 , and a total area, A, of the light exit window, R 1 =A 1 /A, fulfills 0.03<R 1 <0.14.

12 . The luminaire according to claim 1 , wherein, associated with a direction, DR, of the length dimension, x, of the light exit window, defined from the center of the light exit window to the periphery of the light exit window,

sgn

⁢

(

G

1

)

=

+

1

,

sgn

⁢

(

G

2

)

=

-

1

,

and

⁢

G

1

>

❘

"\[LeftBracketingBar]"

G

2

❘

"\[RightBracketingBar]"

>

❘

"\[LeftBracketingBar]"

G

3

❘

"\[RightBracketingBar]"

,

is fulfilled,

and wherein a second portion of the light exit window, defined around the center thereof, has at least one second radial dimension, R b , comprising one of

the second interval, x 2 , and the third interval, x 3 ,

and

the third interval, x 3 .

13 . The luminaire according to claim 12 , wherein the second portion has a second area, A c , wherein a second ratio, R 2 , between the second area, A c , and a total area, A, of the light exit window, R 2 =A c /A, fulfills R 2 >0.86.

14 . The luminaire according to claim 1 , wherein the first interval, x 1 , of the length dimension, x, comprises a change of the luminance, L P , in a range of 10-100%.

15 . The luminaire according to claim 1 , wherein a sum, S, of the first interval, x 1 , and the second interval, x 2 , fulfills 1 cm<S<16 cm.