Lens, corresponding lighting device, lighting installation and method

1. A lens for lighting systems, the lens comprising:

a lenticular body having a planar light input surface and a curved light output surface,

the lenticular body providing a light propagation path from the input surface to the output surface along a lens axis, wherein the lenticular body includes first and second mutually orthogonal sectional planes intersecting at the lens axis, wherein the curvature values of the output surface in the second sectional plane have an average value higher than the average value of the curvature values of the output surface in the first sectional plane; wherein the lenticular body is longer along the first sectional plane than along the second sectional plane;

wherein points of the output surface of the lens have curvature values, with positive curvature values indicative of convexity of the output surface directed outwardly of the lens,

wherein the lens comprises a central region around the lens axis and a peripheral region surrounding the central region, and

wherein the curvature values of the output surface of the lens comprise peak values at the peripheral region and a pair of valley values at the central region between the peak values at the peripheral region; wherein a further peak value at the lens axis is arranged between the pair of valley values; and

wherein the further peak value is equal to or greater than the peak values at the peripheral region.

2. The lens of claim 1 , wherein the further peak value is a mean value for the curvature of the output surface of the lens between the pair of valley values.

3. The lens of claim 2 , wherein the curvature of the output surface of the lens between the pair of valley values extends for a length of at least 20 mm.

4. The lens of claim 1 , wherein the lenticular body is mirror-symmetrical with respect to both the first sectional plane and the second sectional plane.

5. The lens of claim 1 , wherein the curved light output surface is a continuous surface and is free from discontinuity.

6. The lens of claim 1 , wherein the curvature values of the output surface of the lens comprise a difference of at least 0.1 mm −1 between the valley values at the central region and the peak values at the peripheral region.

7. The lens of claim 1 , wherein the curvature values of the output surface of the lens comprise a difference ranging from about 0.1 mm −1 to about 0.3 mm −1 between the valley values at the central region and the peak values at the peripheral region.

8. A lighting device, comprising:

at least one lens, the lens comprising:

a lenticular body having a planar light input surface and a curved light output surface,

the lenticular body providing a light propagation path from the input surface to the output surface along a lens axis, wherein the lenticular body includes first and second mutually orthogonal sectional planes intersecting at the lens axis, wherein the curvature values of the output surface in the second sectional plane have an average value higher than the average value of the curvature values of the output surface in the first sectional plane; wherein the lenticular body is longer along the first sectional plane than along the second sectional plane;

wherein the points of the output surface of the lens have curvature values, with positive curvature values indicative of convexity of the output surface directed outwardly of the lens,

wherein lens comprises a central region around the lens axis and a peripheral region surrounding the central region,

wherein the curvature values of the output surface of the lens comprise peak values at the peripheral region and a pair of valley values at the central region between the peak values at the peripheral region, wherein a further peak value at the lens axis is arranged between the pair of valley values; and wherein the further peak value is equal to or greater than the peak values at the peripheral region; and

a light radiation source coupled with the lens to emit along the lens axis light radiation to propagate through the lens from the light input surface to the light output surface.

9. The lighting device of claim 8 , comprising a light guiding and mixing element between the light radiation source and the lens.

10. The lighting device of claim 8 , wherein the light radiation source comprises:

a plurality of light radiation generators, and/or

light radiation generators of the LED type, and/or

light radiation generators emitting light radiations of different colours.

11. The lighting device of claim 8 , wherein the relative position of the lens and the light radiation source is selectively variable.

12. A lighting installation comprising:

at least one light radiation source to generate light radiation propagating along an axis,

a plurality of lenses, each lens comprising:

a lenticular body having a planar light input surface and a curved light output surface,

the lenticular body providing a light propagation path from the input surface to the output surface along a lens axis, wherein the lenticular body includes first and second mutually orthogonal sectional planes intersecting at the lens axis, wherein the curvature values of the output surface in the second sectional plane have an average value higher than the average value of the curvature values of the output surface in the first sectional plane; wherein the lenticular body is longer along the first sectional plane than along the second sectional plane;

wherein points of the output surface of the lens have curvature values, with positive curvature values indicative of convexity of the output surface directed outwardly of the lens,

wherein the lens comprises a central region around the lens axis and a peripheral region surrounding the central region,

wherein the curvature values of the output surface of the lens comprise peak values at the peripheral region and a pair of valley values at the central region between the peak values at the peripheral region, wherein a further peak value at the lens axis is arranged between the pair of valley values; and wherein the further peak value is equal to or greater than the peak values at the peripheral region;

wherein the plurality of lenses are coupleable to the at least one light radiation source wherein radiation therefrom propagates along said axis from the light input surface to the light output surface of the lens,

wherein the plurality of lenses includes different lenses which differ from one another for the curvature values of the light output surface.

13. The lighting installation of claim 12 , wherein the plurality of different lenses comprises:

at least one first lens having negative curvature values at the lens axis,

at least one second lens wherein the curvature values of the output surface of the at least one second lens comprise a pair of valley values at the central region between the peak values at the peripheral region, with a further peak value at the lens axis.

14. The lighting installation of claim 12 , including a single light radiation source selectively coupleable to different lenses in the plurality of different lenses.