Tubular lighting device

1. A tubular lighting device comprising:

an elongated heat sink;

at least one light source mounted on the elongated heat sink, and

an elongated hollow tubular member with a first and a second end arranged along the elongated heat sink, said tubular member comprising a lens extending between the first and the second end of the tubular member with a light entry surface facing said at least one light source, said lens being adapted to direct light emitted from the at least one light source; and

a light exit surface extending between the first and the second end, the light exit surface being located in front of said lens in a light output direction and the light exit surface having at least one diffusing portion with a transparent portion on each side of each diffusing portion, and

wherein the at least one diffusing portion covers an area on the light exit surface corresponding to a light distribution of said lens projected on the light exit surface, such that the majority of the light emitted by said at least one light source is directed by said lens onto said at least one diffusing portion, and wherein at least a portion of the light emitted by said at least one light source is directed by said lens onto said transparent portions on each side of each diffusing portion.

2. A tubular lighting device comprising:

an elongated heat sink;

at least one light source mounted on the elongated heat sink, and

an elongated hollow tubular member with a first and a second end arranged along the elongated heat sink, said tubular member comprising a lens extending between the first and the second end of the tubular member with a light entry surface facing said at least one light source, said lens being adapted to direct light emitted from the at least one light source; and

a light exit surface extending between the first and the second end, the light exit surface being located in front of said lens in a light output direction and the light exit surface having at least one diffusing portion with a transparent portion on each side of each diffusing portion, and

wherein the at least one diffusing portion covers an area on the light exit surface corresponding to a light distribution of said lens projected on the light exit surface, such that the majority of the light emitted by said at least one light source is directed by said lens onto said at least one diffusing portion, and wherein the at least one diffusing portion has a transmittance which varies along a cross-section of said tubular member.

3. A tubular lighting device comprising:

an elongated heat sink;

at least one light source mounted on the elongated heat sink, and

an elongated hollow tubular member with a first and a second end arranged along the elongated heat sink, said tubular member comprising a lens extending between the first and the second end of the tubular member with a light entry surface facing said at least one light source, said lens being adapted to direct light emitted from the at least one light source; and

a light exit surface extending between the first and the second end, the light exit surface being located in front of said lens in a light output direction and the light exit surface having at least one diffusing portion with a transparent portion on each side of each diffusing portion, and wherein the at least one diffusing portion covers an area on the light exit surface corresponding to a light distribution of said lens projected on the light exit surface, such that the majority of the light emitted by said at least one light source is directed by said lens onto said at least one diffusing portion, and wherein the at least one diffusing portion is located asymmetrically opposite said lens.

4. The tubular lighting device according to claim 1 , wherein the at least one diffusing portion is limited to cover the area on the light exit surface corresponding to the light distribution of said lens projected on the light exit surface.

5. A tubular lighting device comprising:

an elongated heat sink;

at least one light source mounted on the elongated heat sink, and

an elongated hollow tubular member with a first and a second end arranged along the elongated heat sink, said tubular member comprising a lens extending between the first and the second end of the tubular member with a light entry surface facing said at least one light source, said lens being adapted to direct light emitted from the at least one light source; and

a light exit surface extending between the first and the second end, the light exit surface being located in front of said lens in a light output direction and the light exit surface having at least one diffusing portion with a transparent portion on each side of each diffusing portion, and

wherein the at least one diffusing portion (covers an area on the light exit surface corresponding to a light distribution of said lens projected on the light exit surface, such that the majority of the light emitted by said at least one light source is directed by said lens onto said at least one diffusing portion, and wherein the at least one diffusing portion covers less than half the light exit surface.

6. A tubular lighting device comprising:

an elongated heat sink;

at least one light source mounted on the elongated heat sink, and

an elongated hollow tubular member with a first and a second end arranged along the elongated heat sink, said tubular member comprising a lens extending between the first and the second end of the tubular member with a light entry surface facing said at least one light source, said lens being adapted to direct light emitted from the at least one light source; and

a light exit surface extending between the first and the second end, the light exit surface being located in front of said lens in a light output direction and the light exit surface having at least one diffusing portion with a transparent portion on each side of each diffusing portion, and

wherein the at least one diffusing portion covers an area on the light exit surface corresponding to a light distribution of said lens projected on the light exit surface, such that the majority of the light emitted by said at least one light source is directed by said lens onto said at least one diffusing portion, and

wherein the elongated hollow tubular member has a plurality of diffusing portions and wherein the light distribution of said lens is discontinuous so that light is directed towards the plurality of diffusing portions.

7. The tubular lighting device according to claim 1 , wherein the elongated hollow tubular member has one diffusing portion located essentially opposite said lens.

8. The tubular lighting device according to claim 1 , wherein the tubular lighting device has an essentially circular cross-section in a transverse direction of the tubular lighting device.

9. The tubular lighting device according to claim 1 , wherein the lens is a cylindrical lens, having a constant cross-section in a plane normal to a longitudinal direction.

10. The tubular lighting device according to claim 1 , wherein at least one of the elongated hollow tubular member and the elongated heat sink has been manufactured by extrusion.

11. The tubular lighting device according to claim 1 , wherein the tubular lighting device is adapted to be installed in a luminaire for fluorescent tubes.

12. The tubular lighting device according to claim 1 , wherein the light source is a light emitting diode.

13. The tubular lighting device according to claim 1 , wherein the tubular lighting device is a straight cylindrical tubular lighting device.

14. The tubular lighting device according to claim 1 , wherein the lens is in near proximity to the at least one light source.

15. The tubular lighting device according to claim 1 , wherein the lens has a light distribution angle of less than 90°.